Quoted: The bottom line. Get a piston op AR and a direct gas AR. Run them until one stops. You will see th winner. People can argue that direct gas AR's are great. In fact we all know that the AR is an awesome weapon. But History has said it a 1000 times that the direct gas has given reliability issues to the AR15. No doubt! That is a fact. Why cant a piston op system be better. The AK47 is the most reliable assault rilfle in the world. Noone argues that. What is so wrong with  having an AR15 with all of its ergonomics, accuracy, smoothness etc and make it reliable like an Ak??????? People are so scared of change??? Why I do not know other than the tightwad syndrome. If a piston is more reliable( in which it is) why not go with it? The US military is moving towards it. Specops want it Get over it people. It will be the future!!!

Have you ever seen the chamber area of an AK? Or an SKS for that matter? There is LOTS of room there for crap to move around, and it has two large locking lugs (on the AK, the SKS is tilting block) instead of 7 small ones as in the AR. AND it has a bit of "pre-extraction" of the fired case, which has a lot of more taper than the 5.56x45.

The bottom line is that the AK is as reliable as it is not because of the magic piston, but the overall design. I'm a huge AR-15 fan, and honestly consider it superior to the AK, but the AK has some strong points, and the piston is NOT the key to those. Sure, it doesn't hurt, but the clearances in the receiver, cartidge design, strong magazines, are bigger reasons.

If you have a piston-equiped AR, but leave the receiver area the same otherwise, and sand gets in there, the piston is not going to do anything to solve the problem.

When the Danish armed forces tested the Diemaco C7 rifle (basically a hybrid of the A1 and A2), they shot 15,000 rounds with no cleaning, and the things ran fine. The DI system IS dirtier, but it's self-limiting.

Personally, I would rather have a Sig 556 than a pistoned AR-15. Best of both worlds right there.

Quoted: Short Stroke Systems: AR-18 Sig 550 H&K G36 H&K 416 Long stroke: AK-47 FN SCAR FN FNC The SCAR has a short stroke tappet style piston system similar to the M-1 carbine and the M-14. The Sig 550 is a long stroke system similar to the AK.

Ive seen pics of a disassembled SCAR, it looks like a direct impingment system, but I did think the Sig 550 was a short stroke, I havent seen it disassembled though.

I just looked it up, you're right, but take a look at the pic of a SCAR, it does look like a long stroke design. Actually I just looked at a pic of the Sig 550 disassembled, looks like it has an insanely long piston.

So w/ short stroke system, ther is not a direct solid rod that movies the carrier directly, but there are two or more sections of rod that eventually impact the carrier?

SO w/ a long stroke the operating rod is fixed to the piston at one end and directly hits the carrier at the other end?

Quoted: So w/ short stroke system, ther is not a direct solid rod that movies the carrier directly, but there are two or more sections of rod that eventually impact the carrier? SO w/ a long stroke the operating rod is fixed to the piston at one end and directly hits the carrier at the other end?

More or less. Let me explain two basic systems here as not to get too confusing, not to mention Im not an expert here like some claim to be.

On the AK system the piston and bolt carrier are connected, essentially one piece. The gas exits the gas port and hits the end of the piston, which in turn throws the bolt back. very simple and reliable design. On the gas systems being emplyed on the AR there is a gas port which then shoots the gas into a piston which impacts another piston, that then hits the bolt carrier. This results in a cleaner system than the direct impignment system like on the AK.

Quoted: Quoted: So w/ short stroke system, ther is not a direct solid rod that movies the carrier directly, but there are two or more sections of rod that eventually impact the carrier? SO w/ a long stroke the operating rod is fixed to the piston at one end and directly hits the carrier at the other end? More or less. Let me explain two basic systems here as not to get too confusing, not to mention Im not an expert here like some claim to be. On the AK system the piston and bolt carrier are connected, essentially one piece. The gas exits the gas port and hits the end of the piston, which in turn throws the bolt back. very simple and reliable design. On the gas systems being emplyed on the AR there is a gas port which then shoots the gas into a piston which impacts another piston, that then hits the bolt carrier. This results in a cleaner system than the direct impignment system like on the AK.

so in an AK, or presumably any Long stoker, the bolt carrier and op rod are one peice and completely travel together?

And is the piston also connected to the operating rod?

Quoted: Quoted: Quoted: So w/ short stroke system, ther is not a direct solid rod that movies the carrier directly, but there are two or more sections of rod that eventually impact the carrier? SO w/ a long stroke the operating rod is fixed to the piston at one end and directly hits the carrier at the other end? More or less. Let me explain two basic systems here as not to get too confusing, not to mention Im not an expert here like some claim to be. On the AK system the piston and bolt carrier are connected, essentially one piece. The gas exits the gas port and hits the end of the piston, which in turn throws the bolt back. very simple and reliable design. On the gas systems being emplyed on the AR there is a gas port which then shoots the gas into a piston which impacts another piston, that then hits the bolt carrier. This results in a cleaner system than the direct impignment system like on the AK. so in an AK, or presumably any Long stoker, the bolt carrier and op rod are one peice and completely travel together? And is the piston also connected to the operating rod?

I dont know if you would say an AK would have an op rod, I would say they are like one in the same on an AK. Im waiting for somebody with more experience here to chime in. Take a look at a few pics of a field stripped AK and you will see what I mean, plain as day.  I'll see if I can dig up a few pics of the different gas systems and post em back here.

Thanks man

I didn't know that the AK piston was fluted to allow fouling in the actual receiver.  Interesting.  But it is the tolerances and cartridge shape that give it its reliability of course.  

Quoted: I didn't know that the AK piston was fluted to allow fouling in the actual receiver.  Interesting.  But it is the tolerances and cartridge shape that give it its reliability of course.

If you look closely, the .223 Rem cases are tapered, albeit not as tapered as the 7.62x39 case. However, .223 Rem and 5.45x39 cases and .308 cases are not as tapered and the AKs that are chambered to use these cartridges are every bit as reliable as the 7.62x39 AKs. You can scratch out the cartridge shape as being a major contender in making a reliable system.

Wow! Nice educated debate that we are having.
No matter what side of the fence you are on, thats a good thing.

Once again most of the naysayers of the piston AR have never shot one and time will only prove to others that gas piston operated AR15's are more reliable.

I completely understand that its not just the fouling that stops the rifle from functioning. ( I dont agree with the carbon deposits are actuallly working as a lubricant). A piston is a more positive  direct way of cycling the rifle. It is not nearly as sensistive as a direct gas AR.

Yes you should use quality ammunition, mil spec buffers and springs but the piston does not care about what ammo or springs you use. It just keeps shooting.
I have 3 very fine direct gas AR's but there is no doubt that they are not as reliable as my POF.

Piston AR's may not be quite as reliable as an AK because of clearances but by no means would I want to change that. Thats what makes an AR15 what it is. A precision rifle.
I think of a piston operating system as any other upgrade to an AR. Just like a rail , a better stock, oring in the extractor etc.......... If you dont want to spend the money for another reliability upgrade then that is your business.

Heres a couple of pics to help you get an idea:

This is the bolt carrier and gas piston on an AK type rifle, a pic of it is on this page:
http://www.akparts.com/index.htm?c49.htm&1


This is a pic of the short stroke system made by Ares for the AR/M16:
http://www.aresdefense.com/GSR-35/GSR-001.jpg

Quoted: I just looked it up, you're right, but take a look at the pic of a SCAR, it does look like a long stroke design. Thats because you are looking at the operating rod and not the piston itself, the piston is captive with the gas block.  It is a short stroke tappet system.

Thats pretty cool, seems more like a highbrid of the systems. The bolt carrier/op rod looks something like on an AK, but has a short piston up front by the gas block, cool.

Quoted: Quoted: Quoted: The AK uses a long stroke system, any type of piston system that may wind up on an AR will be a short stroke system. This is comparing apples to oranges. The length of the piston's stoke matters fuck all to reliability.  If you think so, explain it in terms that a mechanical engineer (me) can understand, not "I read it on the internet". If you are an engineer then you apparently dont know "fuck all" about guns. The long stroke system does not necessarily refer to the length of the piston's stroke. It refers to a single long one piece piston design like in the AK-47 which is directly impacted by the gas.   The short stroke design is a two or three piece design where a rod impacts another (the piston) which then runs to the bolt and/or bolt carrier (as opposed to the long stroke system where the piston is attached to the bolt carrier like on an AK-47 or the FN FNC and directly impacted by the gas).  Does this explain it in terms that a mechanical engineer can understand, and not "I read it on the internet". Short Stroke Systems: AR-18 H&K G36 H&K 416 Long stroke: AK-47 Sig 550 FN FNC

Just like I thought, you would parrot internet lore and bullshit without providing any credible, technical explanation proving what you claim.

So, just how exactly having a one-piece rod connecting the piston and the bolt make the rifle more reliable?  Higher moment of inertia?  Mechanical advantage?  If so, what multiple?

I love this place.  Someone needs to flush the toilet.  It is overflowing with bullshit.

Quoted: Quoted: Quoted: Quoted: The AK uses a long stroke system, any type of piston system that may wind up on an AR will be a short stroke system. This is comparing apples to oranges. The length of the piston's stoke matters fuck all to reliability.  If you think so, explain it in terms that a mechanical engineer (me) can understand, not "I read it on the internet". If you are an engineer then you apparently dont know "fuck all" about guns. The long stroke system does not necessarily refer to the length of the piston's stroke. It refers to a single long one piece piston design like in the AK-47 which is directly impacted by the gas.   The short stroke design is a two or three piece design where a rod impacts another (the piston) which then runs to the bolt and/or bolt carrier (as opposed to the long stroke system where the piston is attached to the bolt carrier like on an AK-47 or the FN FNC and directly impacted by the gas).  Does this explain it in terms that a mechanical engineer can understand, and not "I read it on the internet". Short Stroke Systems: AR-18 H&K G36 H&K 416 Long stroke: AK-47 Sig 550 FN FNC Just like I thought, you would parrot internet lore and bullshit without providing any credible, technical explanation proving what you claim. So, just how exactly having a one-piece rod connecting the piston and the bolt make the rifle more reliable?  Higher moment of inertia?  Mechanical advantage?  If so, what multiple? I love this place.  Someone needs to flush the toilet.  It is overflowing with bullshit.

The length of the pistons stroke has nothing to do with the reliability because the system being called a "long stroke" has NOTHING TO DO WITH THE LENGTH OF THE PISTON. Which part dont you understand Mr. Engineer?

Well maybe someday we will all grow a brain and have an engineering degree like you and be able to communicate with you. Until then sorry, we'll have to try somehow.

You stated "the length doesnt mean fuck all about reliability", the different systems have nothing to do with length. Go back to engineering school, or maybe take a few more english comprehension classes.

For reliability you dont need an engineering degree to figure out that the direct gas impignment system (aka long stroke) will cause more fouling, loads of crap gets into the AK receiver. This isnt really a problem since the receiver has such loose tolerances. Try some type of direct impignment system on the AR, it would be useless, it would still put almost as much crap into the receiver as the direct gas system. The short stroke system puts NO gases back into the receiver.

Quoted: Actually, what is essentially a long stroke AR system exists, it is the Daewoo K-2 and it gets little fouling into the reciever.

Yeah, but it has to get a hell of a lot more than a short stroke would. Im tlaking about an AK system on an AR, my AK gets loads of crap in it, if my AR had that much crap in it I doubt it would keep going. But again, as said before, apples to oranges, not the same system and almost impossible to compare this way.

Quoted: Quoted: Quoted: Quoted: Quoted: The AK uses a long stroke system, any type of piston system that may wind up on an AR will be a short stroke system. This is comparing apples to oranges. The length of the piston's stoke matters fuck all to reliability.  If you think so, explain it in terms that a mechanical engineer (me) can understand, not "I read it on the internet". If you are an engineer then you apparently dont know "fuck all" about guns. The long stroke system does not necessarily refer to the length of the piston's stroke. It refers to a single long one piece piston design like in the AK-47 which is directly impacted by the gas.   The short stroke design is a two or three piece design where a rod impacts another (the piston) which then runs to the bolt and/or bolt carrier (as opposed to the long stroke system where the piston is attached to the bolt carrier like on an AK-47 or the FN FNC and directly impacted by the gas).  Does this explain it in terms that a mechanical engineer can understand, and not "I read it on the internet". Short Stroke Systems: AR-18 H&K G36 H&K 416 Long stroke: AK-47 Sig 550 FN FNC Just like I thought, you would parrot internet lore and bullshit without providing any credible, technical explanation proving what you claim. So, just how exactly having a one-piece rod connecting the piston and the bolt make the rifle more reliable?  Higher moment of inertia?  Mechanical advantage?  If so, what multiple? I love this place.  Someone needs to flush the toilet.  It is overflowing with bullshit. The length of the pistons stroke has nothing to do with the reliability because the system being called a "long stroke" has NOTHING TO DO WITH THE LENGTH OF THE PISTON. Which part dont you understand Mr. Engineer? Well maybe someday we will all grow a brain and have an engineering degree like you and be able to communicate with you. Until then sorry, we'll have to try somehow. You stated "the length doesnt mean fuck all about reliability", the different systems have nothing to do with length. Go back to engineering school, or maybe take a few more english comprehension classes. For reliability you dont need an engineering degree to figure out that the direct gas impignment system (aka long stroke) will cause more fouling, loads of crap gets into the AK receiver. This isnt really a problem since the receiver has such loose tolerances. Try some type of direct impignment system on the AR, it would be useless, it would still put almost as much crap into the receiver as the direct gas system. The short stroke system puts NO gases back into the receiver.

Nice topic change.

You are utterly unable to explain how having a piston/rod unitized with the bolt increases reliability over a multi part piston/tappet/floating bolt assembly.  So now you confuse an AK's operating system with Direct Impingement?  And now you are in favor of short stroke over long stroke?

Which is it?

Whatever.  Keeping feeding your BS to the uninformed.  Those who actually understand how rifles actually work are laughing at you.

Quoted: Quoted: Quoted: Quoted: Quoted: Quoted: The AK uses a long stroke system, any type of piston system that may wind up on an AR will be a short stroke system. This is comparing apples to oranges. The length of the piston's stoke matters fuck all to reliability.  If you think so, explain it in terms that a mechanical engineer (me) can understand, not "I read it on the internet". If you are an engineer then you apparently dont know "fuck all" about guns. The long stroke system does not necessarily refer to the length of the piston's stroke. It refers to a single long one piece piston design like in the AK-47 which is directly impacted by the gas.   The short stroke design is a two or three piece design where a rod impacts another (the piston) which then runs to the bolt and/or bolt carrier (as opposed to the long stroke system where the piston is attached to the bolt carrier like on an AK-47 or the FN FNC and directly impacted by the gas).  Does this explain it in terms that a mechanical engineer can understand, and not "I read it on the internet". Short Stroke Systems: AR-18 H&K G36 H&K 416 Long stroke: AK-47 Sig 550 FN FNC Just like I thought, you would parrot internet lore and bullshit without providing any credible, technical explanation proving what you claim. So, just how exactly having a one-piece rod connecting the piston and the bolt make the rifle more reliable?  Higher moment of inertia?  Mechanical advantage?  If so, what multiple? I love this place.  Someone needs to flush the toilet.  It is overflowing with bullshit. The length of the pistons stroke has nothing to do with the reliability because the system being called a "long stroke" has NOTHING TO DO WITH THE LENGTH OF THE PISTON. Which part dont you understand Mr. Engineer? Well maybe someday we will all grow a brain and have an engineering degree like you and be able to communicate with you. Until then sorry, we'll have to try somehow. You stated "the length doesnt mean fuck all about reliability", the different systems have nothing to do with length. Go back to engineering school, or maybe take a few more english comprehension classes. For reliability you dont need an engineering degree to figure out that the direct gas impignment system (aka long stroke) will cause more fouling, loads of crap gets into the AK receiver. This isnt really a problem since the receiver has such loose tolerances. Try some type of direct impignment system on the AR, it would be useless, it would still put almost as much crap into the receiver as the direct gas system. The short stroke system puts NO gases back into the receiver. Nice topic change. You are utterly unable to explain how having a piston/rod unitized with the bolt increases reliability over a multi part piston/tappet/floating bolt assembly.  So now you confuse an AK's operating system with Direct Impingement?  And now you are in favor of short stroke over long stroke? Which is it? Whatever.  Keeping feeding your BS to the uninformed.  Those who actually understand how rifles actually work are laughing at you.

Yeah right, everybody here is just laughing up a storm. I admit, im a jackass made a typo, I do know what a direct gas system is, I meant to put in direct piston system. Give it a rest now, lets have some respect here and stop hijacking this thread, sorry everybody.

only one comment.... If the AK is the most reliable rifle in the class, there are several reasons for this that would be above "gas piston" on the list.

First off, Stoner is rolling in his grave.

Quoted: Quoted: I didn't know that the AK piston was fluted to allow fouling in the actual receiver.  Interesting.  But it is the tolerances and cartridge shape that give it its reliability of course.   If you look closely, the .223 Rem cases are tapered, albeit not as tapered as the 7.62x39 case. However, .223 Rem and 5.45x39 cases and .308 cases are not as tapered and the AKs that are chambered to use these cartridges are every bit as reliable as the 7.62x39 AKs. You can scratch out the cartridge shape as being a major contender in making a reliable system.

Not a fair comparison, there are numerous improvement to the AK74 over the AK47/AKM.  Couple of examples, the bolt carrier to bolt weight ratio is more favorable, improved feed ramps, and more efficient extractor.

Quoted: The major drawback of m16/m4/ar15 is on its magazine design rather than its action.

Totally agree

Quoted: Unless you loosen the clearances between bolt carrier and receiver, and bolt lugs and barrel extension, you will not achieve AK 47 reliability.

Totally agree

I originally served with the Galil so I am a big believer in the AK system when it comes to reliability, under any condition. However the Galil with its milled receiver and tough steel mags weighed about 5 kg loaded - and this is without any of the accessories that are so popular these days mounted (unless you include the folding wire-cutter bipod. BTW I don't know if the Galil has the same loose tolerances as the AK, but I always found it to be accurate.

In 94 my reserve unit first switched to M16s during training in the Negev desert in an area with a lot of soft beach-like sand and we experienced a lot of jams. This was apparently a bum bunch of rifles and since then I’ve learned that as long as you make sure that the inside is relatively free of dirt and that you verify that all your mags are functional, the M16 is reliable. Last summer I shot @500 rounds from a relatively new M16A2E3 at the rifle range with no malfunctions.

Last December I was on a 3-day training exercise in the same area. I was issued an M16A1 carbine (14.5 in barrel) that looked pretty beat up and the carry handle was even crushed around the rear sight. It was a Miles-type exercise with no live fire so I carried it with the mag well open the entire time and knowingly neglected it (laid it on the ground, no cleaning etc.). On the last day, after sitting all night and all morning as a forgotten Barrett team on some hilltop with nothing to do, I decided to run an informal, unscientific and formally unsafe sand reliability test.

Pulling it by the sling, I dragged the carbine on the ground a few times with the dust cover open. I then loaded a half full magazine and (pointing the muzzle into the sand in a safe direction), proceeded to manually charge and eject all the cartridges. No problems.

I then took a hand full of sand and poured it into the mag well and racked it a couple of times to work the sand into the action. I could see grains of sand in the barrel extension lugs. Picked the cartridges off the ground, reloaded the mag and repeated the exercise. No problems (didn’t even need to hit the FA).

I picked the cartridges off the ground again and reloaded them into the mag. This time I poured some sand into the mag. Now the problems began, mostly double feeds.

Conclusion: M16 reliability in the sand not as bad as I previously thought and keep the mags clean!

Quoted: First off, Stoner is rolling in his grave. Quoted: Quoted: I didn't know that the AK piston was fluted to allow fouling in the actual receiver.  Interesting.  But it is the tolerances and cartridge shape that give it its reliability of course.   If you look closely, the .223 Rem cases are tapered, albeit not as tapered as the 7.62x39 case. However, .223 Rem and 5.45x39 cases and .308 cases are not as tapered and the AKs that are chambered to use these cartridges are every bit as reliable as the 7.62x39 AKs. You can scratch out the cartridge shape as being a major contender in making a reliable system. Not a fair comparison, there are numerous improvement to the AK74 over the AK47/AKM.  Couple of examples, the bolt carrier to bolt weight ratio is more favorable, improved feed ramps, and more efficient extractor.

I disagree. It is the perfect test.

I'm talking about the same AK design (whatever is currently used in Russia for the RPK) using different calibers: .223 Remington, 5.45x39, 7.62x39, .308 Winchester. It's a perfect test to rule out cartridge shape as the major player in reliability, since you're now testing the cartridge shape in a reliable system (the AK system). The AKs using these cartridges are as reliable as the "7.62x39" AK/RPK. You can blast out .223 from a .223 Vepr all day long and not run into a malfunction.

Comparing cartridge shapes using different rifles is comparing apples to oranges. E.g. "Oh but the 7.62x39 case is tapered so that is why AKs are reliable. Look at how straight .223 is and how it can jam up the AR-15..."

.223 Remington cases do have a taper and are not perfectly straight. Want to see perfectly straight?  5.7x28. 50rd of that stuff double stacked in a totally straight mag. I have not heard of any failures to extract in the P90, which fires full auto at a cyclic rate comparable to the M4/M16, and the same applies to most pistol cartridges like 9mm Luger, 45 Auto.

Quoted: Quoted: First off, Stoner is rolling in his grave. Quoted: Quoted: I didn't know that the AK piston was fluted to allow fouling in the actual receiver.  Interesting.  But it is the tolerances and cartridge shape that give it its reliability of course.   If you look closely, the .223 Rem cases are tapered, albeit not as tapered as the 7.62x39 case. However, .223 Rem and 5.45x39 cases and .308 cases are not as tapered and the AKs that are chambered to use these cartridges are every bit as reliable as the 7.62x39 AKs. You can scratch out the cartridge shape as being a major contender in making a reliable system. Not a fair comparison, there are numerous improvement to the AK74 over the AK47/AKM.  Couple of examples, the bolt carrier to bolt weight ratio is more favorable, improved feed ramps, and more efficient extractor. I disagree. It is the perfect test. I'm talking about the same AK design (whatever is currently used in Russia for the RPK) using different calibers: .223 Remington, 5.45x39, 7.62x39, .308 Winchester. It's a perfect test to rule out cartridge shape as the major player in reliability, since you're now testing the cartridge shape in a reliable system (the AK system). The AKs using these cartridges are as reliable as the "7.62x39" AK/RPK. You can blast out .223 from a .223 Vepr all day long and not run into a malfunction. Comparing cartridge shapes using different rifles is comparing apples to oranges. E.g. "Oh but the 7.62x39 case is tapered so that is why AKs are reliable. Look at how straight .223 is and how it can jam up the AR-15..." .223 Remington cases do have a taper and are not perfectly straight. Want to see perfectly straight?  5.7x28. 50rd of that stuff double stacked in a totally straight mag. I have not heard of any failures to extract in the P90, which fires full auto at a cyclic rate comparable to the M4/M16, and the same applies to most pistol cartridges like 9mm Luger, 45 Auto.

Never mind.

I got a Polytech AK-223, Ive probably put about 3,000 rounds through it. I can count on two fingers how many jams I had with it. And both times it was with crappy Norinco ammo. Ive put less than 1,000 rounds through my AR, and I cant even count on two hands how many misfeeds, and jams Ive had with it. Granted its a DCM model and is extremely picky about what works in it.

To say that the shape of the ammunition is the primary reason for the AK reliability certainly isnt true. I would bet the sharper taper on a 7.62x39 helps, but so does the gas system, and more than anything its inherently loose tolerance design.

Quoted: Conclusion: M16 reliability in the sand not as bad as I previously thought and keep the mags clean!

This coincides with my experience with Taiwanese T65. The malfunctions are mostly due to mags, not the action. However, we were using very dirty ammo with heavy residue and a lot of our M16A1s are clogged with the corrosive residue. Since quality ammo is not a problem for military and civilian shooters in the US, it doesn't really matter for piston or DI ARs.

Mini-14 mags are thinner and hence there is more space between rounds in the mag. Does anybody has torture-tested those Ram-Line Mini/AR mags with an AR?

I have two words for magazine related problems: Magpul followers
The only way to get mag failures with Magpul followers is to use out of spec springs or really worn out springs.

Quoted: I have two words for magazine related problems: Magpul followers The only way to get mag failures with Magpul followers is to use out of spec springs or really worn out springs.

You mean Magpul followers will fix bent feed lips?

I don't think so.

Quoted: Quoted: I have two words for magazine related problems: Magpul followers The only way to get mag failures with Magpul followers is to use out of spec springs or really worn out springs. You mean Magpul followers will fix bent feed lips? I don't think so.

Woops, I forgot about that one!

Quoted: OK guys, I'm not exactly sure how these things work but I have a basic idea.  I still fail to see why they are supposed to be more reliable than a standard gas system.  >SNIP> >SNIP> >SNIP> I want this gun to be the absolute tops in reliability, no exceptions!

OK, I know that no good deed goes unpunished, but I'll take a stab at it...
The Stoner gas system works well for what it was designed to do. The Stoner system is lightweight, uncomplicated and has few moving parts. It is centerline-thrust which is good for accuracy and the opposing forces between the bolt and carrier somewhat unload the bolt locking lugs from the barrel extension prior to bolt rotation. For precision auto-loader shooting, there is in my opinion no better system; i.e. you will probably never see a factory piston for a Knight SR-25/MK 11, MOD 0.

But one of the problems is that assault weapons today are pushed far beyond the intent of the original designers. When a carbine is employed with high-caps and subjected to high rates of firing, failures will become apparent rather quickly. The carbine's high cycle rate increases the load on the bolt carrier, bolt, cam pin, extractor and extractor pivot pin. Because of a carbine's gas port location, it is subjected to significant port erosion. The erosion drives up the cycle rate even further which is why carbines fail sooner than rifles. A cycle rate increase of only a couple-hundred rounds per minute can quadruple the load on all of the moving parts. I won't repeat all of the explanations that have already been offered about heat and fouling in the carrier/receiver group, but I will bring up gas tube deformation and failure under high firing sequences. The direct gas system is also more sensitive to different ammunition types as well as barrel length between the gas port and muzzle. Find Tom Hoel's excellent article in one of the earlier issues of Small Arms Review for an explanation of the physics involved.

Piston systems are more tolerant of heavy firing, shorter barrel lengths; particularly between gas port and muzzle, ammunition types, ambient temperature changes, etc. and they dump their gasses outside of the critical parts of the weapon. Properly designed, they also slow the cycle rate which increases contollability, hit probability and extends weapon component life.

So pistons are a good thing for weapons that will see heavy firing and infrequent cleaning. Since I've gone this far, I'll risk being accused of schilling our product and describe the design-intent behind our GSR-35 Black Lightning piston kit which is superb, and I'll explain some of why we chose the methods that we did.

In the GSR-35, we employ a short-stroke piston and operating rod system for a few basic reasons. One is the space limitation with a standard set of receivers and hand guards. We designed the GSR-35 to fit all standard M4 type carbines and because of this, a long-stroke piston is not practical for a retrofit kit. We chose the "user-installed" retrofit kit approach because we reasoned that most shooters would want to keep their factory barrel, bolt and upper receiver that matches their lower. The military markets would also see value in upgrading their weapons with a low-risk, lightweight, lower priced, armorer-installed conversion.

But the primary reason that we chose a short-stroke piston over a long-stroke piston is that it is more reliable in waterborne operations. Water cannot be compressed; it can only be displaced. Since a long-stroke piston travels the full recoil length of the carrier, water can get trapped in the piston tube and water-lock the carrier causing the weapon to fail. The GSR-35 piston and op-rod only move about 1/2 inch before the spring returns them forward. So water in the cyclinder never hinders the movement of the carrier in either direction.

There is no free lunch however; short-stroke piston designs impact-load the bolt carrier when the op-rod comes into contact with it. We wanted absolute integrity for the carrier and impact key, so we designed the key to be integral with the carrier body; i.e. one piece of steel. Beginning with a 2" diameter bar is not an economical way to manufacture a carrier, but our testing revealed that it was the way to go for absolute reliability, as we managed to destroy every single two-piece design that we tested. We added sand-relief cuts for those heading to the sand-box and increased carrier mass for improved reliability and function.

Next we designed the system to slow the cycle rate for the reasons already described above. In spite of the port erosion that may have already been suffered by an M4, we reduce the gas flow in the components of our kit. So we can take an overcycling M4 with a burned out gas port and reduce it by several hundred RPM. For comparison, watch a video of a standard full-auto M4 and then watch the cycle rate of the GSR-35 equipped M4 in the video linked here: http://www.aresdefense.com/GSR-35/GSR-Beta100.MPG

So, I guess the bottom line is that a sniper or precision shooter will want to stick with a Stoner gas tube system. But, short-stroke pistons are more reliable than direct-gas systems under adverse conditions. They have the benefit of reducing wear and increasing controllability and reliablity in a combat weapon, particuclarly a carbine. But only you can evaluate your own shooting style and decide if a piston or Stoner system is the right thing for you. There are several companies offering their flavor of pistons and if you decide that a piston is the right thing for you, then you should consider the merits of each design and choose one accordingly. -Hope this helps you and others...

Geoffrey
http://www.aresdefense.com

Thanks for the info. Very well explained!

Now the big question. When will your retrofit pistons be available to buy???? You may have a homerun if you can get them to market.

Quoted: Thanks for the info. Very well explained! Now the big question. When will your retrofit pistons be available to buy???? You may have a homerun if you can get them to market.

I'm definitely in line for one.

Now, a question for Ares Defense -- Have you guys figured out a mininmum maintenance schedule for your piston. The LW  system is pseudo self cleaning or something like that. Can your system be cleaned in the field (minimum tool availability). If it can go a few rounds in between cleanings, how corrosion resistant is it?

Not quite as important but have you measured any velocity increase w/ your piston vs the old DI system?

They are already available for $399. Go to their website.

Geoffrey;

So, after all the madness with the Shrike and the recent schedule issues with the GSR you choose to post on AR15.com and tout the merits of your piston conversion.  

I have been interested in the Shrike since I first saw coverage of it in print.  If you can tell me honestly why there has been delays with both products I'd gladly consider purchasing two Shrikes - as I intended to do some time ago.  

If you don't have a good reason for these issues - then, again, tell me so.  

br.