AR Sponsor
[ARCHIVED THREAD] - Gas vs. piston system (Page 1 of 2)
Posted: 3/9/2015 8:53:25 PM EDT
| What are the differences in a gas vs. piston system, pros/cons? Either one better for something or is it just personal preference? |
|
Piston leads to less fouling of your bolt and carrier. Impact is debatable, but average Joes like me will never shoot enough at one time to really see a big impact.
Piston tends to lead to a heavier weapon, overall. Also, most piston bcg parts will not be compatible with standard DI systems. |
| I have both and my experience is that: (i) my piston LWRC rifles are front heavy when compared to DI rifles; (ii) the piston rifles are much easier to clean - whether suppressed or not - than a DI rifle; and (iii) the piston rifles run much cooler than the DI rifles. I really like my LWRC rifles, but you can probably get three decent DI uppers for the cost of one LWRC upper. |
|
Quoted:
I have both and my experience is that: (i) my piston LWRC rifles are front heavy when compared to DI rifles; (ii) the piston rifles are much easier to clean - whether suppressed or not - than a DI rifle; and (iii) the piston rifles run much cooler than the DI rifles. I really like my LWRC rifles, but you can probably get three decent DI uppers for the cost of one LWRC upper. Are piston systems really easier to clean, or is it that you don't see the fouling since most of it is under the front handguard and not on the BCG and in the Upper Receiver? |
|
They are easier to clean. Fouling on the inside of the handguard has zero effect on function. The rest is vented forward. There is a small amount of fouling that enters the action from the open chamber, but that's maybe 5% of what you get from a DI gun.
In most cases you don't need to do anything to the action other than wipe the BCG with a cloth and then re-lube it. You rarely need to disassemble the BCG because it's not getting fouled from the inside. |
|
Some differences that I can see are as previously noted: heavier upper receiver assemblies, non-interchangeable parts on piston system guns (not just not-interchangeable with DI guns, piston systems are not standardized, so parts from/on other makers pistons guns won't fit either), much higher price on piston guns (2X-3X).
Other things to consider: carrier tilt has been a problem on some piston guns (requiring more non-interchangeable parts to be added), and since the excess gas vents at the front gas block, the handguards get very hot pretty quick on piston guns (not a problem when firing just a few shots off a bench at the target range, but under sustained fire on the two way range, will be a problem unless shooter is wearing gloves). Each different piston gun, requires a set of spare parts that only fit on that gun if you are into having spare parts to minimize downtime. In the case of SHTF, you're going to need more guns or at least more uppers that you can switch to in order to take advantage of the supply of standard parts that fit DI guns. Your piston guns are going to become non-op as parts break or wear out, when there aren't any replacement parts available. If you have a DI gun, most any part from a standard M-16 or AR-15 made from the beginning of time will fit, and function (with the exception of semi-auto parts stuff in a auto gun making it semi-auto, OR auto parts dropped into a semi-auto gun (will not make it a auto)), changing from a carbine to a rifle or rifle to a carbine stock (need to change the buffer and spring too), AND the Colt AR-15 large pin/small pin thing. |
|
I have 4 of each and I'll take my piston ARs over DI for the following reason
less oil needed because the BCG doesn't get as dirty and IMO more reliable better for SBRs which is why I also believe its more reliable better for suppressors because you have less blow back in your face they are just as accurate. better for water...maybe because you don't have to drain the gas tube only down sides to a piston are slightly more felt recoil that I counter with a heavier buffer slightly heavier up front which doesn't bother me proprietary parts Carrier tilt isn't an issue with current quality pistons |
|
Quoted:
They don't help with suppressors. Most of the back pressure comes through the bore / chamber (larger hole = path of least resistance). they do help with suppressors. I have shout them both with suppressors 2 areas of gas coming back to the BCG is worse than one and if you're saying it doesn't than the BCG wouldn't cycle 
|
|
easier to clean because they don't heat up as much and get dirty
which means less oiling test them yourself take a DI and GP with standard BCGs and short (10 inch) barrels Then spray them down with something that takes all the oil/grease off Then take under powered ammo like wolf Then shoot a few hundred rounds with out oiling them I'd put money on the piston lasting longer 
I suspect most of the pro DI AR15 say they like the DI better because they don't have or ever shot a quality |
|
Quoted:
Are piston systems really easier to clean, or is it that you don't see the fouling since most of it is under the front handguard and not on the BCG and in the Upper Receiver? Quoted:
Quoted:
I have both and my experience is that: (i) my piston LWRC rifles are front heavy when compared to DI rifles; (ii) the piston rifles are much easier to clean - whether suppressed or not - than a DI rifle; and (iii) the piston rifles run much cooler than the DI rifles. I really like my LWRC rifles, but you can probably get three decent DI uppers for the cost of one LWRC upper. Are piston systems really easier to clean, or is it that you don't see the fouling since most of it is under the front handguard and not on the BCG and in the Upper Receiver? My experience has been that the piston uppers are significantly cleaner than the DI models. I can clean a piston upper in about 1/3 the time that I can clean a DI upper. Unless I shoot suppressed, the BCG in my piston uppers don't even show any visible fouling. A quick wipe with CLP on a patch generally does the job on the BCG on my piston rifles. In contrast, my DI rifles require that I strip the bolt and get pretty detailed before the powder is removed. The barrel also seems to require more cleaning with the DI rifles. Cleaning a piston upper just seems like a real plus for someone like me who generally doesn't find gun cleaning therapeutic. If you lived in Miami, I'd gladly show you the difference. Of course, you'd have to clean the rifle to fully appreciate it! Just saying. |
| I completely agree with a piston system doesnt solve problems associated with running suppressed ars. I had similar experience and got gas to face issues and dirty chamber after doing some mag dumps in my piston ar. I say stay with DI and run an adjustable gas block to help manage excessive gas. Fyi, I am running a adams arms piston system with 11.5 voodoo barrel and 762 specwar suppressor. |
|
First we should get our terminology right. The "standard" AR is NOT direct impingement; it has a piston. It is correctly referred to as the Stoner gas system. What people refer to as a "piston system" simply means that there is a piston at the end of the operating rod, which is rigidly attached to the carrier, as in an AK, FAL, M1 Garand, etc. A true DI system lacks a piston.
Now, as has been mentioned, the op rod system doesn't really help with receiver fouling versus the Stoner system when using suppressors, as the extreme majority of the blowback comes through the chamber, not the tiny gas port and tube. And, of course, in non-suppressed use, the Stoner system just isn't that dirty. IMO, the op rod systems for ARs are a solution in search of a problem. They add weight, create new issues (aforementioned carrier tilt), and complicate matters with proprietary parts. They have no place in my collection. |
|
Quoted: easier to clean because they don't heat up as much and get dirty which means less oiling test them yourself take a DI and GP with standard BCGs and short (10 inch) barrels Then spray them down with something that takes all the oil/grease off Then take under powered ammo like wolf Then shoot a few hundred rounds with out oiling them I'd put money on the piston lasting longer I suspect most of the pro DI AR15 say they like the DI better because they don't have or ever shot a quality Piston guns heat up just as much as DI. Heat comes from friction and explosive gases. Both systems fire the same ammunition, which emits the same explosive gases and experience the same friction of the projectile in the barrel. The barrels and gas blocks are what experience the harshest heat, in both systems. I suspect most of the pro piston AR15 say they like the piston better because they are ill-informed and fall for marketing gimmicks. |
|
Quoted:
You sound like someone who has fallen for all of the piston hype and misinformation. Piston guns heat up just as much as DI. Heat comes from friction and explosive gases. Both systems fire the same ammunition, which emits the same explosive gases and experience the same friction of the projectile in the barrel. The barrels and gas blocks are what experience the harshest heat, in both systems. I suspect most of the pro piston AR15 say they like the piston better because they are ill-informed and fall for marketing gimmicks. Quoted:
Quoted:
easier to clean because they don't heat up as much and get dirty which means less oiling test them yourself take a DI and GP with standard BCGs and short (10 inch) barrels Then spray them down with something that takes all the oil/grease off Then take under powered ammo like wolf Then shoot a few hundred rounds with out oiling them I'd put money on the piston lasting longer
I suspect most of the pro DI AR15 say they like the DI better because they don't have or ever shot a quality Piston guns heat up just as much as DI. Heat comes from friction and explosive gases. Both systems fire the same ammunition, which emits the same explosive gases and experience the same friction of the projectile in the barrel. The barrels and gas blocks are what experience the harshest heat, in both systems. I suspect most of the pro piston AR15 say they like the piston better because they are ill-informed and fall for marketing gimmicks. oh stop.... I have owned pistons since my first lwrc in 08 and it's not even close. the wear, heat, gas, carbon etc etc is far less in a piston. The question is 'will this matter in the limited situations and amount of pills downrange most of us use our rifles for' and not about easier to clean. lwrc has a video of the system during their 100k test which shows the heat mostly located near the piston release vs the di where it's down the gas tube and back at the bcg area. |
|
I'm no long term expert by any means, but I haven't seen that horrible, nasty, residue that is supposed to be the norm for a DI gun...at least non-suppressed...no experience with suppressors. My two AR's are DI in AR10 platforms. Even after a couple of hundred rounds fired in a session, I've been quite surprised how clean the chamber, barrel throat, and bolt are for a cleaning. From a lot of comments here, I expected some pretty nasty results. Now, I don't run anything nastier in ammo in these two rifles than Winchester and Federal in those "white" boxes in 7.62X51, so maybe that helps.
Is this a statement for DI superiority over piston?...NO. I have a 5.56 Steyr Aug and a 5.56 Kel-Tec PLR that are both piston...love 'em. I don't think I'd let piston or DI be my final point for making a choice among many quality guns out there. |
|
Quoted:
easier to clean because they don't heat up as much and get dirty which means less oiling test them yourself take a DI and GP with standard BCGs and short (10 inch) barrels Then spray them down with something that takes all the oil/grease off Then take under powered ammo like wolf Then shoot a few hundred rounds with out oiling them I'd put money on the piston lasting longer
I suspect most of the pro DI AR15 say they like the DI better because they don't have or ever shot a quality You really believe that most choose DI because they have never shot a quality rifle? That is absurd. |
|
Pistons are good but again I don't know that they would be that much better than a DI gun. Unless you are going to run through 1000 rounds full auto, is there a benefit? I've seen vid's of Noveske's doing it so a DI gun could do it anyway.
I run a POF recon 16" barrel and it's a heavy ass stick. My other fav is a KAC 16" and I like it just as much and it's much lighter and shoots just as straight. Both have weapon specific parts, I have never seen carrier tilt but it has an enhanced buffer tube to prevent it. POF is easier to clean but it does get fouling under the front handguard around the gas block. The piston is every bit as tough to clean as the bolt and carrier on the DI gun. The biggest difference that I notice outside the weight is on the Piston. I run triple taps on both of them and the Piston is a flamethrower compared to the DI gun. I assume that is due to the bulk of the gas leaving out the barrel, however I don't know for sure. They are both great and I love shooting both. Piston gun was my 2nd AR and I have bought nothing but DI since.  " />
 " />
|
|
What I've observed over the years in classes?
Pistons are heavy, recoil harder, and more prone to be unreliable. I have seen precious few, or no, experienced shooters run, or recommend any piston other than a 416. That's clue. The exception to that is an H&K 416. |
|
Quoted:
oh stop.... I have owned pistons since my first lwrc in 08 and it's not even close. the wear, heat, gas, carbon etc etc is far less in a piston. The question is 'will this matter in the limited situations and amount of pills downrange most of us use our rifles for' and not about easier to clean. lwrc has a video of the system during their 100k test which shows the heat mostly located near the piston release vs the di where it's down the gas tube and back at the bcg area. Quoted:
Quoted:
Quoted:
easier to clean because they don't heat up as much and get dirty which means less oiling test them yourself take a DI and GP with standard BCGs and short (10 inch) barrels Then spray them down with something that takes all the oil/grease off Then take under powered ammo like wolf Then shoot a few hundred rounds with out oiling them I'd put money on the piston lasting longer
I suspect most of the pro DI AR15 say they like the DI better because they don't have or ever shot a quality Piston guns heat up just as much as DI. Heat comes from friction and explosive gases. Both systems fire the same ammunition, which emits the same explosive gases and experience the same friction of the projectile in the barrel. The barrels and gas blocks are what experience the harshest heat, in both systems. I suspect most of the pro piston AR15 say they like the piston better because they are ill-informed and fall for marketing gimmicks. oh stop.... I have owned pistons since my first lwrc in 08 and it's not even close. the wear, heat, gas, carbon etc etc is far less in a piston. The question is 'will this matter in the limited situations and amount of pills downrange most of us use our rifles for' and not about easier to clean. lwrc has a video of the system during their 100k test which shows the heat mostly located near the piston release vs the di where it's down the gas tube and back at the bcg area. I think AR10's generally shoot cleaner than AR15's, at least mine does, but I don't get that much fouling from my AR15's lately either. Was used to getting a caked layer of carbon on the bolt but regular lube seems to slow that down. Never shot a piston AR. |
|
Quoted: oh stop.... I have owned pistons since my first lwrc in 08 and it's not even close. the wear, heat, gas, carbon etc etc is far less in a piston. The question is 'will this matter in the limited situations and amount of pills downrange most of us use our rifles for' and not about easier to clean. lwrc has a video of the system during their 100k test which shows the heat mostly located near the piston release vs the di where it's down the gas tube and back at the bcg area. Quoted: Quoted: Quoted: easier to clean because they don't heat up as much and get dirty which means less oiling test them yourself take a DI and GP with standard BCGs and short (10 inch) barrels Then spray them down with something that takes all the oil/grease off Then take under powered ammo like wolf Then shoot a few hundred rounds with out oiling them I'd put money on the piston lasting longer I suspect most of the pro DI AR15 say they like the DI better because they don't have or ever shot a quality Piston guns heat up just as much as DI. Heat comes from friction and explosive gases. Both systems fire the same ammunition, which emits the same explosive gases and experience the same friction of the projectile in the barrel. The barrels and gas blocks are what experience the harshest heat, in both systems. I suspect most of the pro piston AR15 say they like the piston better because they are ill-informed and fall for marketing gimmicks. oh stop.... I have owned pistons since my first lwrc in 08 and it's not even close. the wear, heat, gas, carbon etc etc is far less in a piston. The question is 'will this matter in the limited situations and amount of pills downrange most of us use our rifles for' and not about easier to clean. lwrc has a video of the system during their 100k test which shows the heat mostly located near the piston release vs the di where it's down the gas tube and back at the bcg area. |
|
Since I personally have never had any reliability issues with my direct gas impingement system AR-15s, my interest in a gas piston system is due mainly to curiosity. (Isn’t that what killed the cat?) The possibility of having to spend less time cleaning the bolt carrier group and upper receiver is also rather appealing.
Proponents of the gas piston system for the AR-15 claim it is more reliable than the direct impingement system, (which seems rather ironic since the gas piston system not only adds more parts to the overall system, but adds more moving parts as well.) Opponents of the gas piston system state the AR-15 does not have reliability issues as long as proper cleaning and maintenance procedures are followed. They also claim that the gas piston system causes a decrease in the accuracy of the AR-15. There are a few different gas piston systems for AR-15s on the market, but most of them are proprietary affairs. The allure of the Ares Defense GSR-35 is that it is user installable on your existing AR-15. The GSR-35 kit comes with everything you need to convert your existing system to a piston system, including a set of modified M4 handguards. 
You use the bolt from your existing system but remove the gas rings to run with the gas piston system. I chose to use a Smith Enterprise chrome plated bolt as this would more easily show the fouling on the bolt for comparison. I also chose to use a 16” HBAR for my testing and evaluation of the GSR-35 with the rationale that a heavy barrel would be the least likely profile to show a decrease in accuracy (if it actually did occur). If a substantial decrease in accuracy was found using the gas piston system with an HBAR, there would be no point in even testing the system with a government profile or light-weight profile barrel. The 16” HBAR I used for the conversion is a new chrome-moly barrel (not chrome lined) of uncertain pedigree. (I think it was made from a Douglas blank, but it’s been sitting on my spare parts shelf for so long I’m not sure.) The barrel is stamped as having a 5.56mm chamber and a 1:9” twist. Upon removing the GSR-35 kit from the box, I was disappointed to see that the gas spigot was bent. It was only slightly angled away from the gas cylinder, but you would think Ares Defense would hold a higher level of quality control on such a crucial piece of their system. The Ares defense literature states their gas system is designed to work with “mil-spec” AR-15s. I decided to deviate a bit from the “mil-spec” by using a JP Enterprises adjustable gas block, for three reasons. 1.The JP gas block uses an extra long roll pin to secure the gas tube/gas spigot. I thought this would help to mitigate any problems with the roll pin walking-out during firing, (as has been reported.) 2.The JP gas block is secured to the barrel using set screws. I wanted to see if a set screwed gas block could withstand the additional forces applied to it by a gas piston system. 3.The JP gas block is adjustable. I thought this might prove for some interesting experiments if the gas piston system proved useful. (The gas adjustment was left “wide open” for this evaluation.) Before installing the GSR-35 system on my carbine, I performed some informal accuracy testing from a distance of 50 yards using the direct impingement gas sytem. The forearm of the rifle was placed on a sandbag resting on a wobbly table. There was no support for the butt-stock (nor for my elbows.) The ammunition used was one of my hand-loads, using Sierra 52 grain MatchKings and VihtaVuori N135 powder. As well as being an extremely accurate load, this load has functioned flawlessly in every AR-15 I own. I fired three 10-shot groups in a row that measured, 0.558”, 0.408”, and .570” for an average group size of 0.512”. The targets are pictured below. 
Dennysguns has done a great job of describing the installation of the GSR-35, so I’ll not go into that here. As I mentioned earlier, the gas spigot from my kit was slightly bent. When installed on the carbine, this caused the gas cylinder to angle very slightly to the starboard side of the barrel. This in turn caused some very slight binding at the juncture of the gas cylinder/gas piston/connecting link. before conversion 
after conversion 
I began function testing of the newly converted carbine by loading and then firing a single round at a time from a magazine for the first ten rounds and then 3 rounds at a time for the next several magazines. I experienced multiple failures of the bolt to lock back after the last round of the magazine was fired. I don’t know if this was do to the slight binding of the mechanism I mentioned above, or if the system just needs a little “breaking in.” After approximately 30 rounds the bolt began to lock back consistently. There were no further malfunctions during testing. I performed informal accuracy testing with the GSR-35 system installed on the carbine in the same manner as described above. The three 10-shot groups that I fired from 50 yards measured, 0.677”, 0.501” and 0.879” for an average of 0.685”. (targets pictured below) This does demonstrate a decrease in accuracy (larger average group size) using the gas piston system compared to the direct impingement system, albeit a rather small one at approximately 0.35 minutes of angle with this 16” HBAR. 
I fired a total of 90 rounds for this first test session of the GSR-35 and here is what the bolt and carrier looked like afterwards; (pictured below) not nearly as much fouling as would have been present with a direct impingement system. Below is a picture of the inside of the upper hand-guard. This is where the fouling goes with the gas piston system. I was pleased to note that the JP gas block had not shifted forward at all during testing; nor was there any sign of rotational shifting. Also, the roll pin securing the gas spigot held tight. 
Over the next few months, I plan to fire 1,000 rounds of ammunition from the GSR-35 converted carbine without cleaning the gas system. If there are no further malfunctions/problems, I will be doing some formal accuracy testing of the system from 100 yards. If the results from that testing are acceptable, I’m going to repeat this course of testing with a GSR-35 installed on a 16” government profile barrel. Here’s a pic of my GSR-35 carbine. 
The highest part of the GSR-35 above the barrel on my carbine is the section on the gas cylinder just aft of the spigot. It's the shiny spot on the gas cylinder with the red arrow pointing to it in the picture below. The shiny spot was caused by the gas cylinder rubbing against the the underside of the upper handguard. 
Here are some pics showing the differences between the two sets of handguards from the inside. 
Today I fired 90 rounds through one of my direct impingement 16” uppers. Here are some pics showing the Smith Enterprise bolt carrier group from that upper compared to the Ares GSR-35 bolt carrier group after firing 90 rounds. 
I fired an additional 89 rounds through the Ares equipped carbine without a single malfunction. When pulling the trigger on the 90th round, all I heard was the dreaded “click.” I kept the carbine pointed downrange for 20 seconds and then examined the ejection port. The bolt had failed to close completely on the round going into the chamber. The bolt carrier still had 1/8" to 1/4" of forward travel to go. I dropped the magazine and attempted to clear the chamber by pulling back on the charging handle, several times. The action was locked up tight. The lugs on the bolt had just barely started to turn and therefore were engaged with the lungs of the barrel extension. I finally had to slam the buttstock against the ground while pulling on the charging handle to clear the weapon. At that point, I chose to pause the testing until I could determine the cause of the malfunction. Upon returning home, a quick visual inspection of the bolt carrier group, chamber and gas system revealed no obvious abnormalities. I cycled a couple of dummy rounds through the action with no malfunctions. I next turned my attention to the cartridge involved with the malfunction. I dropped the cartridge into a JP Enterprises chamber gauge and the cause of the malfunction became painfully clear. The cartridge failed to completely seat in the gauge. Here is a pic of a cartridge properly seated in the chamber gauge and then one of the cartridge that caused the malfunction. 
Scharch case. 
I checked the headspace of the abnormal cartridge using an RCBS Precision Mic. The headspace measured +0.008”. That’s 8 thousandths of an inch longer than nominal headspace for the caliber. Obviously the case had not been properly resized and that is why it failed to completely chamber in the Ares carbine. I checked the headspace on the remaining 30 rounds that I had loaded for this test session and found two more cases that were not properly resized. Since RVO is no longer a reliable source for once-fired and resized Lake City cases, I had decided to give the once-fired and resized cases from Scharch Mfg. a try. That is the source of the cases that I had used in this test session. This is the first time that I have ever had one of my hand-loads fail to chamber. Since I am confident that the malfunction was due to the ammunition and not the Ares gas system, testing will continue. However, I will be chamber checking all the cases before heading to the range. Here’s a pic of the bolt and carrier after a total of 180 rounds fired. 
300 rounds I fired another 120 rounds through the Ares equipped carbine today without a single malfunction. (I used virgin Lake City brass for the handloads this time.) Here are a couple of pics showing the bolt/carrier group and Ares gas system after a total of 300 rounds. 
The inside of the lower receiver looks as if it has hardly been used. The magazines are still remarkably clean also. Just for kicks (and to prove a point) I fired some 75 grain A-MAX loaded rounds from the Ares upper from a distance of 25 yards. The 10-shot group is pictured below. Check out the key-holing! 
400 rounds I fired another 100 rounds through the Ares upper today without a single malfunction. After a total of 400 rounds there has been no walking-out of the gas tube pin nor any movement of the JP Enterprises gas block. Something I noticed today after doing some close range reflexive shooting drills is that the handguards seem to heat up quicker with the Ares system than with the DI system; particularly near the front of the handguards where the gas vents from the gas cylinder. I may have to invest in an infrared thermometer to determine if this is actually the case. Here is a pic of the bolt and carrier group after the accumulated 400 rounds of firing and below that a pic showing a comparison from the individual test sessions. 
One of the attractive aspects of the Ares unit is that you can easily convert back to the DI system if you so desire with no adverse affect to your weapon (and then use the Ares unit to convert another DI system to the piston system if you like.) It's too soon for me to make recomendations for the system. For example, I perceived the handguards heating up quicker with the Ares system in my recent test session. I don't know what affect, if any, this will have during extended shooting sessions or long term usage. For my next test session I plan to put a lot more rounds downrange in one outing. I will tell you this, I definitely like the decreased fouling in the receivers and bolt carrier group. Also, while there may be a slight decrease in accuracy when using the Ares system, the accuracy is still more than adequate for my intended use. In the last test session I fired the 10-shot group pictured below from 50 yards in an informal accuracy check, using handloaded 55 grain V-MAX bullets. The group measures 0.632”. While not minute of angle, it is certainly good enough for government work. 
550 rounds I ran 150 rounds through the Ares upper today without a single malfunction for a total of 550 rounds. The bolt is getting fouled at this point, but I can still see shiny chrome on it! 
700 rounds Another 150 rounds went through the Ares upper today with almost monotonous reliability. That makes a total of 700 rounds through the Ares upper with no additional malfunctions since the 180th round. Remember, that malfunction was due to the ammunition. Using the Ares upper and 55 grain FMJ handloads, I fired a quick 10-shot group from 50 yards on a 300 yard E2 silhouette target reduced for 50 yards. The results are pictured below, showing that while the Ares system might not produce MOA accuracy, it is certainly good enough for practical shooting situations even when using FMJ rounds. 
Here's a pic of the bolt carrier group after 700 rounds. 
800 rounds 800 rounds and counting with no further malfunctions to report. 200 rounds to go! 
920 rounds As I mentioned in a previous post, I wanted to let the Ares carbine sit idle for a few weeks without cleaning as part of the testing. I've read that even the gas piston on the AK can freeze-up and need a little kick start on the charging handle if the weapon is not fired for a while. So, after letting the carbine sit for 4 weeks I headed back to the range. I fired another 120 rounds through the upper without a single malfunction. At this point, I decided to end the reliability testing. I didn't think another 80 rounds would uncover any new problems that haven't been discovered in the last 920 rounds and I was eager to begin the formal accuracy testing. Here's a pic of the bolt carrier group after 920 rounds. 
Here's a compilation of bolt carrier group pics. 
Here's a look at the bolt carrier group broken down. Look at the tail on that bolt! Did you ever see one so clean after firing 920 rounds? 
Most of the fouling on the bolt and carrier was wet fouling and wiped off with a paper towel. The rest came off with a little Break-Free and a nylon brush. There was none of the typical cacked-on, hardened carbon fouling normally encountered when cleaning a direct impingement AR-15. Here's a look at the Ares gas system after 920 rounds. 
Here is the gas system broken down. 
I was surprised as to the absence of cacked-on carbon fouling on the gas piston and in the gas cylinder. Again, this fouling came off easily with some Break-Free and a nylon brush. The gas spigot did have the typical hardened carbon fouling on it, but that would not normally be removed from the gas block for cleaning. Here's a close up of the gas piston after 920 rounds. 
Here's a pic showing the inside of the gas cylinder after 920 rounds (it was difficult to get a decent picture of the inside of the cylinder.) 
Here's where a lot of the fouling from the Ares system ends up; deposited on the inside of the handguards. 
On a totally unrelated note, here's what 1040 rounds of brass tracking on the case deflector look like. 
As a recap of the reliability testing of the GSR-35, my unit experienced multiple failures of the bolt to lock back during the first 30 rounds. After the initial 30 rounds, there was no further occurence of this malfunction. Round number 90 failed to go into battery, but this was conclusively determined to have been caused by the ammunition. No other malfunctions occured from that point on. 100 Yard Accuracy Test Formal accuracy testing of the Ares carbine upper was done following my usual protocol. Three 10-shot groups were fired from a distance of 100 yards off a concrete bench using front and rear bags to support the rifle. A Leupold VARI-X III was used for sighting. The ammunition used was one of my standard handloads using Sierra’s 52 grain MatchKing. Wind conditions were monitored using a “Wind Probe” (and it’s a good thing because it was quite windy during testing.) I fired three 10-shot groups in a row from the Ares carbine with the extreme spread of the groups measuring: 1.04” 0.99” 1.20” The average extreme spread for these three groups is 1.08”. This is right on par with what my direct impingement 16” Colt HBARs will do. 
The three 10-shot groups from the Ares upper were overlayed on each other using RSI Shooting Lab to form a 30-round composite group. The mean radius for this composite group was 0.32”. The composite mean radius of three 10-shot groups fired from my 16” Colt HBAR was also 0.32”! Shown below is a comparison of the accuracy of the Ares upper with three different 16” Colt barrels. 
This Is Rumor Control There have been a lot of rumors floating around the Internet (including some on this web-site) that gas-piston uppers possess some magical ability to propel a bullet “up to 200 fps faster" than a direct impingement upper with the same length barrel. A simple application of science shows this is not the case. I converted the Ares upper I’ve been using in the testing for this thread back to a direct impingement upper (16” barreled, carbine gas system upper.) Using hand-loaded 69 grain Sierra MatchKings, I fired three 10-shot strings of this ammunition over my Oehler 35-P chronograph positioned 21 feet from the muzzle. I let the barrel cool and then converted the DI upper back to a gas-piston upper using the Ares GSR-35 system. Now, using the exact same barrel with the gas-piston conversion and the exact same lot of hand-loaded ammunition, I fired three more 10-shot strings over the chronograph, for a total of 30 rounds through each different gas system. Here Are The Facts 
As you can see from the table above, using 30-round samples for comparison, there is only a 7 fps difference between the direct impingement gas system and the Ares gas-piston system when using the same ammunition and the same 16” barrel. Temperature- 63 degrees F Humidity - 34% Barometric pressure – 30.20 Elevation - 960 feet above sea level Winds – variable Skies – partly cloudy, Jupiter aligned with Mars Government Profile Barrel Testing For the next phase of testing of the Ares GSR-35 gas piston conversion, I wanted to install the unit on a government profile barrel. I chose one of my Colt 6922 barrels as the test vehicle. (The 6922 is a 16” M4 profile barrel with a 1:9” twist.) Ares GSR-35 on Colt 6922 
The first thing I noticed when installing the Ares unit on this barrel is that the gas spigot binds on a portion of the barrel near the front sight base. This did not occur with the heavy barrel that I used in the original test. One has to wonder what effect this might have on accuracy. Arrow indicating area where gas spigot binds with barrel. 
Original HBAR setup without any barrel binding. 
I wanted to use a free float hand-guard with this set-up to avoid the problem of the unit binding on the Ares M4 hand-guards. Since Ares still has yet to release their “upside-down KAC” free-float rail designed for this unit, that was not an available option. The only commercially available free-float hand-guard that I’m aware that will work with the Ares unit without requiring an alteration of the hand-guard is the A.R.M.S. SIR system. I used the #50 slim-line, bi-level military version SIR. The highest portion of the Ares unit clears the underside of the SIR rail by approximately 0.030”. A.R.M.S. SIR with Ares GSR-35. 
100 Yard Accuracy Comparison Prior to installing the Ares GSR-35 unit on the 16” M4 barreled upper with the ARMS SIR free-float rail, I tested the accuracy of that upper in its direct impingement configuration from a bench-rest at 100 yards. Using hand-loaded 52 grain Sierra MatchKings, three 10-shot groups were obtained which had extreme spreads of: 1.59”, 1.55” and 1.73” for a 10-shot group average extreme spread of 1.62". While not the most accurate barrel I own, it’s still perfectly suitable for “government work.” The three 10-shot groups were over-layed on each other using the RSI Shooting Lab software program to obtain a 30-round composite group. The mean radius of the composite group was 0.54”. After the upper was converted to the GSR-35 piston system, accuracy testing continued in the same manner as above. Three 10-shot groups were obtained using the same load of 52 grain Sierra MatchKings. Those groups had extreme spreads of: 1.77”, 2.54” and 1.85” for an average 10-shot group extreme spread of 2.05". The mean radius of the 30-round composite group created from those three groups was 0.69”. This demonstrates a decrease in accuracy of approximately 0.45 MOA for the ARES system. 
On the outside chance that the increase in group size was caused by the Ares configuration simply “not liking” the 52 grain MatckKing load, I fired an additional three 10-shot groups using a hand-load of 55 grain V-MAX bullets charged with a different powder. Those groups had extreme spreads of 2.65”, 2.14” and 1.78” for an average 10-shot group extreme spread of 2.19" with a 30-round composite mean radius of 0.72”. As I mentioned earlier on this page, one has to wonder if the Ares unit binding against the barrel is having a negative effect on accuracy.
Shortly after conducting the accuracy evaluation, the Ares upper began to have failures of the bolt to lock back after the last round in the magazine was fired. Next, I noticed that the cases were being ejected less effectively to the point that they were just barely falling out of the upper receiver. Finally, the upper completely failed to cycle. I hand cycled a few rounds that fired but my Ares upper was now a one-shot AR-15! After a quick examination of the gas piston system, I found that the gas tube pin had been sheared in half and the gas spigot had shifted slightly in the front sight base causing a misalignment with the gas port. I haven’t used the small spring that is supposed to go in the gas tube channel from the period after my initial testing was completed since it was initially reported that the spring is not needed on the newer units, so this is the most likely cause of the shearing of the gas tube pin. ARES later clarified that “the small spigot spring (is) essentially obsolete in most cases when the kit is installed in a standard carbine. If the sheet metal handguard cap is not used such as with some rail forends, then the spigot spring must be used to eliminate impact loading of the retaining roll-pin. 
Here is a pic of the underside of the ARES M4 handguard showing the the channel worn into the heat sheild from rubbing against the gas cylinder. 
Also interesting to note, is that when I installed the ARMS SIR on the upper with the ARES system, there was a definite clearance between the gas cylinder and the underside of the SIR rail. Yet, after firing there were clearly signs on the underside of the SIR rail that the ARES gas cylinder had been making contact with it during the firing cycle. 
..... |
| In theory piston ARs are more reliable, but I haven't seen anything that backs that up. My Direct Gas Impingement AR is reliable. I have yet to have any failure. I've seen gas piston ARs fail. Although Adam's Arms have a good track record I've heard. Just stick with DI and never look back. |
|
Quoted:
I have both and my experience is that: (i) my piston LWRC rifles are front heavy when compared to DI rifles; (ii) the piston rifles are much easier to clean - whether suppressed or not - than a DI rifle; and (iii) the piston rifles run much cooler than the DI rifles. I really like my LWRC rifles, but you can probably get three decent DI uppers for the cost of one LWRC upper. Is the benefit worth installing on a suppressed rifle? |
|
Quoted:
instead Is the benefit worth installing on a suppresed rifle? Quoted:
Quoted:
I have both and my experience is that: (i) my piston LWRC rifles are front heavy when compared to DI rifles; (ii) the piston rifles are much easier to clean - whether suppressed or not - than a DI rifle; and (iii) the piston rifles run much cooler than the DI rifles. I really like my LWRC rifles, but you can probably get three decent DI uppers for the cost of one LWRC upper. Is the benefit worth installing on a suppresed rifle? . no Get an adjustable gas block, war upper, and a gas buster ch |
|
Quoted:
Ive never seen an internal piston ar (which the uninformed call di) jam and thought "man, an external piston/op rod would have kept running" Save your money, stick with stoners internal piston Ca,me here to say this. My INTERNAL PISTON AR's function very well. I started off with the original design, then a few years ago decided to jump I to a "external piston" upper (AA), then ditched the AA and went back to the original. They weigh less, have less moving parts and function just fine. YMMV op |
|
Quoted:
Are piston systems really easier to clean, or is it that you don't see the fouling since most of it is under the front handguard and not on the BCG and in the Upper Receiver? Quoted:
Quoted:
I have both and my experience is that: (i) my piston LWRC rifles are front heavy when compared to DI rifles; (ii) the piston rifles are much easier to clean - whether suppressed or not - than a DI rifle; and (iii) the piston rifles run much cooler than the DI rifles. I really like my LWRC rifles, but you can probably get three decent DI uppers for the cost of one LWRC upper. Are piston systems really easier to clean, or is it that you don't see the fouling since most of it is under the front handguard and not on the BCG and in the Upper Receiver? Depends on the system I would imagine, but the Adams Arms piston system is unbelievably easy to clean and you don't even have to take the handguards off. Also, there is a (imho) perceivable difference in muzzle rise on my AAM4 vs most middys I've fired with birdcages on both guns. Of course, that could just be perception. |
|
I have both and enjoy shooting both. I can't tell a difference in accuracy, but I can tell a difference in how clean the piston rifle stays. I tend to doubt if that makes a practical difference or not if properly lubed.
My AA piston was built before the existence of the WAR upper or decent adjustable gas blocks. I bought the conversion because I was getting a face full of gas when shooting the 11.5" barrel suppressed. With my rifle, it most assuredly reduced the gas in the face and made it much more pleasant to shoot. There is absolutely NO DOUBT about that. The gun was and has been reliable in either configuration and has been used in both configurations in several 1000+ round courses. So, in total I found: No increase or decrease in reliability. The weight difference was negligible IMO. Especially when the heavy suppressor is hanging off the end. Slightly cleaner running with the piston but this might not make much difference unless you didn't clean for multiple thousands of rounds. I couldn't tell any accuracy difference. Definitely less gas in the face when shooting it (SBR) suppressed. Other options to reduce gas in the face are available now so if I had to make my choice today, I might be more likely to try something like the WAR upper. |
|
I think Molon's post very eloquently solidified my opinion that piston ARs are shit.
Clean bolts are of absolutely no consequence. A thousand measly rounds without cleaning is nothing. I've gone upward of 7K in dusty conditions and only wiped off the bolt then because it had over 10K and I was changing gas rings as a preventive measure.. The ONLY malfunctions I've EVER had have been mag related. And they were precious few, related to one or two early Gen M2 Pmags that had been beat all over Texas. There is some merit to the 10.5" H&K 416. Other than that, unnecessary. |
|
one thing not mensioned here is carreir tilt with the piston uppers. my LWRC uppers show a little of this on the bottom edge of the buffer tube.
i would have to say the pistons are nice to keep power fouling down but even a piston BCG needs lube and wont run 100% when dry so with that, its not much of an advantage over DI. now an AK, FNC, daewoo, robinson or SCAR in 223 is a different animal. in my opinion, if you want an AR get a DI and save the money and just keep it lubed and clean it once in awhile. |
|
Quoted:
i would have to say the pistons are nice to keep power fouling down but even a piston BCG needs lube and wont run 100% when dry so with that, its not much of an advantage over DI. But a piston BCG keeps its lube way longer than a DI, because it isn't being constantly being blown off with hot dirty gas being injected from the inside. |
|
Quoted:
But a piston BCG keeps its lube way longer than a DI, because it isn't being constantly being blown off with hot dirty gas being injected from the inside. Quoted:
Quoted:
i would have to say the pistons are nice to keep power fouling down but even a piston BCG needs lube and wont run 100% when dry so with that, its not much of an advantage over DI. But a piston BCG keeps its lube way longer than a DI, because it isn't being constantly being blown off with hot dirty gas being injected from the inside. If you lube it enough, it's a non issue. Gob the CLP, or Slip, or whatever in there and it'll run all day (500+ rounds) no problem. Done it many many times. Suppressed will generally want more lube. |
|
Quoted:
But a piston BCG keeps its lube way longer than a DI, because it isn't being constantly being blown off with hot dirty gas being injected from the inside. Quoted:
Quoted:
i would have to say the pistons are nice to keep power fouling down but even a piston BCG needs lube and wont run 100% when dry so with that, its not much of an advantage over DI. But a piston BCG keeps its lube way longer than a DI, because it isn't being constantly being blown off with hot dirty gas being injected from the inside.
|
|
Quoted:
But a piston BCG keeps its lube way longer than a DI, because it isn't being constantly being blown off with hot dirty gas being injected from the inside. Quoted:
Quoted:
i would have to say the pistons are nice to keep power fouling down but even a piston BCG needs lube and wont run 100% when dry so with that, its not much of an advantage over DI. But a piston BCG keeps its lube way longer than a DI, because it isn't being constantly being blown off with hot dirty gas being injected from the inside. 
|
|
Quoted:
I think Molon's post very eloquently solidified my opinion that piston ARs are shit. Clean bolts are of absolutely no consequence. A thousand measly rounds without cleaning is nothing. I've gone upward of 7K in dusty conditions and only wiped off the bolt then because it had over 10K and I was changing gas rings as a preventive measure.. The ONLY malfunctions I've EVER had have been mag related. And they were precious few, related to one or two early Gen M2 Pmags that had been beat all over Texas. There is some merit to the 10.5" H&K 416. Other than that, unnecessary. 
Not sure how you derived that from Molon's post (which as always is an excellent objective test). Malfunctions experienced are clearly attributable to the Ares design an not an indictment of all piston systems. My DI rifles work well. My piston rifle works well. One is significantly easier to clean than the other. My LWRCI spr is slightly heavier in the front end than a DI rifle with similar barrel profile. Recoil with the LWRC is slightly sharper than a DI rifle of similar weight (can be addressed via heavier buffer). |
|
Quoted:
I think AR10's generally shoot cleaner than AR15's, at least mine does, but I don't get that much fouling from my AR15's lately either. Was used to getting a caked layer of carbon on the bolt but regular lube seems to slow that down. Never shot a piston AR. Quoted:
Quoted:
Quoted:
Quoted:
easier to clean because they don't heat up as much and get dirty which means less oiling test them yourself take a DI and GP with standard BCGs and short (10 inch) barrels Then spray them down with something that takes all the oil/grease off Then take under powered ammo like wolf Then shoot a few hundred rounds with out oiling them I'd put money on the piston lasting longer
I suspect most of the pro DI AR15 say they like the DI better because they don't have or ever shot a quality Piston guns heat up just as much as DI. Heat comes from friction and explosive gases. Both systems fire the same ammunition, which emits the same explosive gases and experience the same friction of the projectile in the barrel. The barrels and gas blocks are what experience the harshest heat, in both systems. I suspect most of the pro piston AR15 say they like the piston better because they are ill-informed and fall for marketing gimmicks. oh stop.... I have owned pistons since my first lwrc in 08 and it's not even close. the wear, heat, gas, carbon etc etc is far less in a piston. The question is 'will this matter in the limited situations and amount of pills downrange most of us use our rifles for' and not about easier to clean. lwrc has a video of the system during their 100k test which shows the heat mostly located near the piston release vs the di where it's down the gas tube and back at the bcg area. I think AR10's generally shoot cleaner than AR15's, at least mine does, but I don't get that much fouling from my AR15's lately either. Was used to getting a caked layer of carbon on the bolt but regular lube seems to slow that down. Never shot a piston AR. On an AR10 possibly running cleaner than an AR15, can anyone comment some more on that? I'm asking, not claiming anything. |
|
Quoted:
Not sure how you derived that from Molon's post (which as always is an excellent objective test). Malfunctions experienced are clearly attributable to the Ares design an not an indictment of all piston systems. My DI rifles work well. My piston rifle works well. One is significantly easier to clean than the other. My LWRCI spr is slightly heavier in the front end than a DI rifle with similar barrel profile. Recoil with the LWRC is slightly sharper than a DI rifle of similar weight (can be addressed via heavier buffer). Quoted:
Quoted:
I think Molon's post very eloquently solidified my opinion that piston ARs are shit. Clean bolts are of absolutely no consequence. A thousand measly rounds without cleaning is nothing. I've gone upward of 7K in dusty conditions and only wiped off the bolt then because it had over 10K and I was changing gas rings as a preventive measure.. The ONLY malfunctions I've EVER had have been mag related. And they were precious few, related to one or two early Gen M2 Pmags that had been beat all over Texas. There is some merit to the 10.5" H&K 416. Other than that, unnecessary.
Not sure how you derived that from Molon's post (which as always is an excellent objective test). Malfunctions experienced are clearly attributable to the Ares design an not an indictment of all piston systems. My DI rifles work well. My piston rifle works well. One is significantly easier to clean than the other. My LWRCI spr is slightly heavier in the front end than a DI rifle with similar barrel profile. Recoil with the LWRC is slightly sharper than a DI rifle of similar weight (can be addressed via heavier buffer). If 'running clean' was somehow advantageous, I would consider it an advantage. Sine it has no bearing on any functional aspect of the gun, I won't. I've ran my ARs filthy for years and NEVER had a stoppage due to fouling. Straight sand, in an upper, yes. Fouling? Never even close. |
|
Quoted:
If 'running clean' was somehow advantageous, I would consider it an advantage. Sine it has no bearing on any functional aspect of the gun, I won't. I've ran my ARs filthy for years and NEVER had a stoppage due to fouling. Straight sand, in an upper, yes. Fouling? Never even close. Quoted:
Quoted:
Quoted:
I think Molon's post very eloquently solidified my opinion that piston ARs are shit. Clean bolts are of absolutely no consequence. A thousand measly rounds without cleaning is nothing. I've gone upward of 7K in dusty conditions and only wiped off the bolt then because it had over 10K and I was changing gas rings as a preventive measure.. The ONLY malfunctions I've EVER had have been mag related. And they were precious few, related to one or two early Gen M2 Pmags that had been beat all over Texas. There is some merit to the 10.5" H&K 416. Other than that, unnecessary.
Not sure how you derived that from Molon's post (which as always is an excellent objective test). Malfunctions experienced are clearly attributable to the Ares design an not an indictment of all piston systems. My DI rifles work well. My piston rifle works well. One is significantly easier to clean than the other. My LWRCI spr is slightly heavier in the front end than a DI rifle with similar barrel profile. Recoil with the LWRC is slightly sharper than a DI rifle of similar weight (can be addressed via heavier buffer). If 'running clean' was somehow advantageous, I would consider it an advantage. Sine it has no bearing on any functional aspect of the gun, I won't. I've ran my ARs filthy for years and NEVER had a stoppage due to fouling. Straight sand, in an upper, yes. Fouling? Never even close. that pretty much sums it up. a DI will run a long time as long as the fouling is kept wet with oil. |
|
Give me a BCM Middy .... the piston AR's can stay home
I wouldnt mind a LWRC and have always wanted one but I personally dont see the advantages "Cost, Proprietary Parts". Especially if you have multiple DI AR's already..... IMHO I would rather get a Tavor if anything  that would seem to have more value for the money to me.
|
[ARCHIVED THREAD] - Gas vs. piston system (Page 1 of 2)
AR Sponsor