Just like to hear why or is it worth getting a gas piston upgrade for AR-15? I know what it does the gas piston makes the AR-15 more reliable and less pron to problems cause by the carbine build. Not that is not enough but would like to know more about the system does it affect anything else? Can I use it on a 300 BLK upper? and I use the same hand guards that I have now or do they take special hand guards? Does the gas piston work well with a can?

Any advice would help thanks!

I'll give you my $0.02 especially since you are asking about pistons and suppressors. I have tried several different piston and adjustable gas systems; in my experience with looking for a SBR (>10.5") suppressor host that will run reliably with multiple ammo types, the AA piston won out.  

The AA system works and most of the hype is true: runs cleaner (not really true, the gunk just vents in a different place.) increases reliability (over the DI carbine gas system) with various ammo types.   These traits are more pronounced with SBR setups and suppressor use.  The AA system with its half-gas setting greatly reduces that amount of blowback (does not eliminate it though) and fouling in the upper receiver.  An adj gas block (Switchblock, variable gas block, etc...) does a similar function and reduces that overgassing but still introduces a tremendous amount of carbon fouling in the upper receiver.  

Depending on which system you decide on will drive your choices on handguards.  If you go with a AA system, I recommend using a two piece handguard because this will allow cleaning behind the gas block (where the gas/crud vents) without needing to remove the gas block.  AA has a new kit called XLP which does fit under several rails.

Due to the fast burning powder, pistons do not offer an advantage or play well with 300BLK (in my experience, tried it).

Fatkid

There are many legacy DI fans who are passionate about DI. I am not one of those people. That is why my first rifle was an AK. Now that piston ARs are available and performing well, I own two piston ARs. Read below:

Sgt. Charles Perales of Fort Bragg, NC had this to say in a letter reprinted by Defense News:

   “My unit – B Company, 2nd Battalion, 504th Parachute Infantry Regiment – was deployed to Afghanistan from April 2005 to March 2006. While there, we were attached to Special Forces at Camp Tillman on the Afghan border… I saw first-hand what happens when your weapon jams up because of the harsh environments we have to call home there. An 18B weapons sergeant was shot in the face due directly to his weapon jamming. I just can’t believe that after things like this happen, the Army is still buying more M4s.

http://www.defenseindustrydaily.com/the-usas-m4-carbine-controversy-03289/

Any advantage you can have with your rifle is good. Especially in harsh conditions, keeping fouling away from your action will only improve your chances of survival. My choice, Colt 6940P, they have the piston thing right with their design.

Limited experience, so treat this as a single data point. I own *one* piston setup, an Adams Arms mid-length kit, mounted on a mid-length Green Mountain barrel. It has been flawless in operation with a variety of loads ranging from M855 to Tula/Herters to handloads from min to max; lubrication lasts twice as long; perceived recoil is lower. It is heavier, and the weight is on the front. It requires a metal back-up sight, so your cheap MBUS are out. I've seen zero evidence of carrier tilt. If the Apocalypse were tomorrow, this is the setup for which I'd reach. That is all.

IMHO.
Check out Lewis Machine Tool. Excellent rifles, fit and finish best I have seen and great customer service. They are tack drivers.

I have the Faxon ARAK-21 and the upper can be chambered for .223/5.56, .300 BLK, .308, and just announced 7.62x39mm.

The ARAK 21 happens to be one of the more expensive uppers starting at $1200 and $1500 for two carbon steel barrels of your choice plus the upper, however since it a self contained upper, there is no chance of carrier tilt and you have the option of a folding stock. It has an ambidextrous, non-reciprocating charging handle and works on any mil-spec AR-15 upper.

Moves most of the gunk out of the reciever.

But I still get black crap in the reciever and on the bolt

Of course I shoot suppressed mostly

Less blow back when shooting suppressed.  Gemerslly

There is no compelling reason why you should. There is no compelling reason why you shouldn't.
There are drawbacks and benefits to both DI & GP.

My personal reason as to why I choose GP;  it seems more logical to me to have all the hot gases, unburnt powder, carbon, and fouling being pushed out the front of the gun as opposed to having a fraction of it redirected back towards my face, into the BCG, and out the side of the bolt.

Why sweep dirt back into the house if you don't have to?

Less cleaning is one reason. But then again some pistons can be a pain to clean too.
My Ruger, as the only piston, has been the most reliable AR at our club (the others are DI). But it is not like DI AR's malfunction often anyway. I think the biggest difference is in how they shoot. I prefer piston over DI. I find the recoil easier to manage, more predictable and even. It also shows in the ejection pattern as all my brass ends up nicely in a pile. But in the end it comes down to personal preference imho. So you need to try both out to compare and choose what you like best.

As a piston fanboy I'm 100% convinced it's the way to go.  I can't even tell whether it's a piston or not and it doesn't really change anything for me.  Come cleaning time it's the best thing ever.  In an extreme situation, it makes for a cleaner, cooler chamber.  I can't think of any mechanical device on the planet that improves with heat and dirt. And if you think of it, the DI is a design hiccup surrounded on both sides by piston systems.  Which of the two has been copied, and which one never.  Now you put a little more room around the BCG and you'll have an accurate AK.

Buying my first AR I went with a Sig 516. It had everything I wanted in an AR: great furniture, piston system that I read was the newer tech and cleaner, etc., and it's proven to be a fantastic rifle. I have never had an issue with it. However, the AR bug is real and I'm wanting to do more with it and customize it a bit. That's where I'm finding problems. Because of the proprietary piston system, I'm limited on furniture. I'm wanting a full-length hand guard, but Sig doesn't have them and the only option I'm finding is one by Lancer, and I don't like the looks of it. I want a 15" M-Lok hand guard. They're available for any DI gun, but I can't find another option for the guard or low-profile gas block.

ARs get dirty so you need a system that will smack the fuck out of the BCG to make sure it cycles good and hard. Might be hard on the gun it fuck it, no amount of carbon can stop it.

I run AK's, 2 AA piston AR's, and 1 DI AR. I'm a fan of piston operating systems, HOWEVER... not really a fan of them on AR's.
Here's why. The lock up design is NOT meant for a piston system. What I mean by this is that a DI bolt gets pushed FORWARD by the incoming gas ... which THEN (since the bolt cannot go further forward) pushes the bcg back. This creates a liner movement backwards and forces the bolt to rotate out of battery WHILE being pushed FORWARD by the expanding gas (as the bcg moves rearward). They "oppose" each other during unlock. With a piston AR... no. There is no FORWARD pressure on the bolt (sorry, that silly AA bolt spring does nothing. It's no match to 30k psi of gas pressure of DI), so when the bcg get tapped back by the rod, it then PULLS (unlike a DI's push) the bolt rearward against the BE lugs (not good, and something the DI does NOT do). It's a serious flaw for piston AR systems.
Does it work? Yes. But only due to superior materials of parts. You could also shift your manual trans clutchless and it would hold up.... for a while. But still not sound principle.
I love AK's and all piston systems (even enjoy my AA AR's), but IMHO, piston AR's are an improper mashing of parts (not sound engineering) unlike an AK's properly designed system.
For this reason, by clean AA piston AR's are range toys, while my DI AR is my HD.
Edit: exception to ARAK, but it's not an AR at ALL. It is simply a properly designed piston system upper that happens to utilize an AR LOWER.

How does the BCG unlock on a piston set up? I'm picturing it but can't quite figure out if the bolt unlocks due to the rearward push on the carrier and the cam pin forcing it out from the cut out on the carrier or if the bolt unlocks because the cam pin hits the inside of the receiver cutout. I know with an AK for instance the bolt unlocks because the lug engages a groove on the carrier which when the carrier is pushed rearward, forces the bolt head to turn and then residual gas pressure past the unlocking stage forces the BCG rearward.

Everything I build and what I have built for others has been with the AA Piston.  Other than the need for nostalgia I only see 2 advantages of the DI system, and one isn't really a systemic advantage anyway...

1. DI moves the recoil impulse in line with the rifle rather than above or below it.  If I were a 3-gunner coming off a target requiring 2 rounds is a disadvantage, so the linear impulse is an advantage.  Frankly though with the current designs of brakes and comps on the market this has about been eliminated as an advantage.

2. Availability of parts of the DI system.  If the zombie appocolypse comes and your stick goes down there are far more DI pieces to find and replace/repair yours.

So that's about it.  I see no other advantages to DI.

On the other hand for pistons:

1. Moves the heat and nastiness outside of the operational system of the firearm.  The DI s4!+$ where it eats.  This cannot be conducive to extending time between needed maintenance.  

2. Lube.  DI eats lube because of #1.  everyone tells you to "run it wet!"  I run grease.  I brake clean it out about twice a year and that's probably too often.  The grease stays where it's supposed to be and doesn't drip, run, or spatter.  To a lefty like me this is especially important because of where the ejection port is I get oil all over my eye protection from a wet DI gun.  Piston running grease does not do this.

3.  Plays nicer with suppressors.... period.  The piston is less finicky with changes in power of ammo, and the asjustability of essentially all pistons on the market allow gas levels to be set based on what you're shooting and if it's suppressed.  A suppressor adds significantly to #1 as well.

4.  It's much cooler.  DI guys argue that "it just moves the heat."  That is correct.  They send gas and heat back down the barrel where it belongs.  A little escapes from the piston themselves, but the majority passes back through the block with the return of the piston to its starting position and exits the barrel, like gasses should.  It also means after a mag dump you can pull the BCG and it hasn't chenged in temp at all.  Do that with a standard BCG and if you aren't wearing welding gloves you'll very quickly know what the smell of seared human flesh is.

5. Simplicity.  There is a reason essentially every other battle rifle and assault rifle runs a piston... it works.  No rifle should fail because you jimmied up the ten cent rings on the back of the bolt.  No rifle should fail because screws came loose or worse sheared and caused a gas leak on top of the BCG.  Solid BCGs don't fail.

I'm sure I'm not thinking of something but those are some of the biggies to me.

Jhend, weight and balance are in favor of DI and external pistons have piston rings too.

I'd also argue simplicity sits in the camp of the DI design. It is a simple gas tube, no extra moving parts.

That being stated, I still enjoy the externalized piston setups. No reason one cannot enjoy both.

I kind of get the first post, but it disproves itself as the AK, SCAR 16 & 17, G36 and a host of other pistons use a rotating bolt head to pull the bolt out of battery, and on all it does not involve the lugs.  As for DI VS Piston, they both unlock by rearward forces on the BCG.  Since the bolt is passive as it's in lock up, it only goes where it's pulled.  You can not have a net zero physical process--period.  The push to the front on the DI is not a zero effect, the gas forces the only thing that will move, which is the BCG, and it yanks it out of battery.  
The major force against the lugs occurs upon firing, and is not negated by gas, as the gas doesn't get to the chamber until the bullet clears the port hole.  Whether the charging handle, rod, gas, or your finger--it easily pulls out of battery as the cam pin action easily rotates it past the lugs. There is no additional damaging force in a piston system, as either way the bolt is twisted out of the way.  
The spring on an AA is not intended to provide anything as far as return anything as that is handled by the big ole spring in the stock, which also doesn't handle 30K of pressure--again the lugs and chamber walls and what flies down the barrel take that force.  

Not quite. In an AK, the rear bolt lugs are tapered to rotate the bolt as it is pulled back (don't forget, other piston designs use cammed bolts and RAILED bcg's, not a cam pin design). The AR has squared lugs. Huge difference. Also, no, the DI works by PUSHING the bolt forward (and continues to do so as the bcg moves REARWARD until the bolt rings clear the "vent holes" in the bcg. That forward pressure on the bolt is essential, as it does two things:
1) it forces the bolt to press against the chamber during unlocking, instead of being pulled against the locking lugs as it rotates out (the cam pin turns it while it is still pressing FORWARD on the chamber).
2) it aligns the cam into the grove BEFORE it contacts the rear of the "cutout" (which is why "cam pin gouge" is common in piston versions, while NOT in DI versions. Piston versions rely on the cam pin, itself, via contact, to rotate the bolt, where as a DI uses opposing gas pressure and the cam pin clears into the channel without needing to contact it).
People keep forgetting (and it rarely mentioned) that a DI does not just push the bcg back, it also pushes the bolt FORWARD (that is a critical part that a piston version cannot replicate).
An AK (and other various piston systems) do not NEED to have opposing forces, because they are designed (via lobes/ramps, camming surfaces, etc) to operate in a REARWARD only manner. The AR DI is not designed this way. It is designed to use opposing forces.
As I've said, the piston versions work (provided you use high quality components), but they are not a proper design by any means.

ETA: someone will probably point out that there is no opposing forces when manually cycling a DI AR, and that is true. But that is also done at minimal speed and without the pressure of a round being fired (thus why DI's get MINOR scuffs there, while a piston version often suffers from "gouging").
Don't get me wrong, I enjoy my two AA piston rifles, but am well aware of the "less than proper" engineering utilized for them to operate.

You are right, but you forgot one very important factor. In "DI" pressure inside cylinder (bolt carrier) pushing piston (bolt) forward is significantly lower than chamber pressure that pushes bolt lugs against receiver extension lugs. BTW this is one of reasons why ammo with longer duration pressure peak (eg. Hornady Superformance) is not recommended to use in AR15 with carbine length gas system (unless adjustable gas block is in use), due to high chamber pressure at unlocking.

Point 2 is absolutely right, but also can be solved in "piston" rifle by small changes to upper receiver (relief cut) and adding firing pin return spring that also pushed bolt slightly forward (not really that important, but helps a bit).

If those issues were significant, then using external, op-rod piston system in place of internal, in-line piston system in AR15 would be unfeasible or would be subject to dramatically reduced bolt on extension lugs life. This is not true.

Going back to original questions, I like to use guidance for using op-rod (external) piston system derived from Larry Vickers. If 1 of following points are true "piston" should be considered, if 2 it is recommended, if more than 2 it is almost mandatory:

1. Barrel shorter than 14.5".
2. Shooting a lot in full auto.
3. Shooting a lot with suppressor.
4. Shooting a lot in extreme environments.
5. Limited ability to keep weapon clean and well lubed.

There is also one additional point, my own and eat beats all other:

6. Just because I want to have piston AR. Period!

There is no reason to get a piston AR.  If you want a piston gun, get a gun designed around a piston operating system, and take full advantage of it.    If you want an AR, get direct impingement.   It is lighter, it has less reciprocating mass, and the bullshit about how it "shits where it eats" is negligible for 99% of the users, including those who use it in a professional capacity.

I disagree........that is all.

A piston gun should have a square carrier.

The reciprocating mass argument is rather silly because the BCG/buffer/spring must have the same combined X amount of energy to provide for reliable striping and chambering of the next round in both DI and GP.

Think about it in terms of extremes, the kinetic energy of a 100mph fastball is .5*.328lbs*100^2, or 1640 (whatevers).  An average car weighs 3280 lbs and would have the same kinetic energy (1640 whatevers) as the baseball when traveling 1mph.  Between these two, which would you be able to bring to a stop with your hand with more with more control?  Obviously the car.  Hence, more mass isn't necessarily a bad thing.

With proper attention paid to each variable a blanket statement that "more reciprocating mass = bad" just isn't correct.

Piston system are proven in combat to be incredibly reliable. Case in point the H&K 416, which is known for its reliability and its ability to fire under any condition. Others include FNH Scar, AK platform, GAP-10, LWRC REPR, Bad News 338, Benelli Shotguns and others that are incredible machines.

Piston systems a lot of the time have an adjustable gas block, so not only do they work with a can, they can be shut off. Want to take that 308 out deer hunting with a suppressor on it? Not a problem you can run it with the system turned off and reduce the overall weapons report. Or you can turn it up to allow more gas to flow with the subsonic rounds and get a better system feed. They work just fine with suppressors.

Things to note. A lot of conversion systems have caused people problems. So be weary of conversions.

You will hear that it messes up the recoil direction this is completely false. Many gas piston systems are known to be easier to follow up shot with. They tend to be heavier, this can be good or bad. Weight improves accuracy, and your ability to hold the weapon steady, but also increases fatigue. It also reduces recoil.

Its well known piston systems keep heat down, and keep weapons cleaner. Also piston systems take a heavier toll on optics. So cheaper optics wont be advisable.

Not to nit-pick but I think you mean it is well known they move heat to a different location. The gas block gets VERY hot still but the carrier won't get hot.

Take a look at some durability test videos of the AR piston setups, while at dusk, you can see some glowing red blocks.

Yes I meant overall your not feeding hot gas back in to the chamber and through the system. Sure the gas block has to eat some of it, and the piston itself will as well. But your not feeding it directly back to the bolt and chamber.

Correct, the heat and carbon are STILL present, just deposited in a different location.
The piston set up really shows it's benefit when the weapon is suppressed.

So DI bolt lugs never break due to the recoil pressures put upon them ?    Ive heard this opinion before but never have seen any type of valid evidence of a serious flaw. Tell me the types of pressures applied to the bolt lugs of each type of system , has there been any side by side long term testing of bolt life for each system ? what are the ratios of failure and the causes of failure ?

Many of the issues attributed to DI guns have to do with the carbine length gas system. With the short gas tube, extraction begins to occur prior to chamber pressure being reduced. The extra wear on the extractor is greatly reduced by utilizing a mid length or rifle length DI gas or piston system. External pistons work better with suppressed guns because the back pressure can be tamed easier with the external piston setup. Same issue with SBR's... carbine length tube.

In regards to the pressure on the lugs in a DI gun the poster above mentioned several times, the fact you are missing is that the 55,000 psi you speak of pushing against the lugs while it is locked up is minimal compared to the surface area of case wall pressing against the chamber with 55,000 psi of force. A poorly timed external gas piston system doesn't even have enough force to pop that case out of the chamber until enough time has passed for the case pressure to subside so this should give you an idea there is almost no pressure on the lugs. (Got an extractor ripping right through the bullet rim, leaving the case stuck in the chamber? You are over-gassed or gassing too quickly-see carbine length gas system issue above)

The other poster above is correct in that the "pinging" action of a short stroke piston system puts tremendous pressure on the lugs prior to the cam pin rotating them far enough to clear the extension lugs. In a DI gun, there is NO rear pressure on the lugs from carrier movement. The bolt face is pushing against the chamber as the cam pin is unlocking. Only after the cam pin is fully rotated and the carrier is unlocked does the carrier continue rearward. Think swimmer pushing off the edge of the pool. Only when the swimmers legs reach the fully extended position do his feet, and his entire body, move away from the wall. The one-piece carrier, increased strength bolt lugs, roller cam pins, and anti-tilt bulges at the rear of the carrier are all solutions to problems encountered in retrofitting the DI system to external piston.

The idea of a much cooler bolt carrier with an external piston is greatly exaggerated as evidenced here: LINK REMOVED- It appears his site is down but google Vuurwapen POF temp. He tested piston vs. DI temps and the piston carrier was only a few degrees cooler. The POF barrel nut had more impact on the chamber temp than the external piston. JP Enterprises may be onto something with their thermal disapator but I digress.

Piston systems DO have MUCH cleaner bolt carriers. This is EXTREMELY ammo dependent though. Carbon on the firing pin or the back of the bolt is virtually non-existent after thousands of rounds with the EP setup. And with worn DI piston rings, more carbon will make it to the lugs. Although carbon on the lugs is not eliminated with the external piston system, the pressure against the lugs as they are rotating actually keeps carbon scraped off the lugs where it counts. Also, well designed EP's for the most part have self-cleaning pistons that continually scrape the carbon off and will require almost zero maintenance unless you are using very dirty or corrosive ammo.

I own both piston and DI guns and I am realistic about the pro's and con's of both systems. SHTF use? I hate to say it but probably one of my DI AR's with a mid length gas system. With the external piston setup you are usually adding an additional spring and two or three additional moving parts, which according to Murphy, just gives you 3 or 4 more things that can fail. Of course for the zombie apocalypse I'll have an Otis bone tool for scraping carbon off the bolt and firing pin, and the biggest bottle of Slip EWL oil I can fit crammed inside my magpul grip. Oh and I need to mention my DI guns have NP3 coated bolt carriers, which stay a lot cleaner and require less lube to keep going with higher round counts.

So what's your thoughts on the pws long stroke system paired with an Adams arms bolt spring.

The GAP-10 is DI and the REPR had issues in DEA service.

Most quick adjust gas blocks can't be turned off and not all piston guns work with suppressors. The SureFire 556K suppressor had to be redesigned into the -212 because it choked the 416.

It's been my experience that short stroke guns have a fast, harsh and dramatic recoil impulse that lifts the reticle off of the target--and then the reticle settles right back to where it was. If your timing is good you can shoot very well with them. If you pull the trigger fast you might have a problem.

With a can on the gas goes right back down the bore and fouls the gun whether it has a piston under the handguard or in the action.

Definitely the long stroke piston system is going to put less pressure on the lugs. The short stroke works like hitting the bolt carrier with a punch and a hammer. The lugs receive all the stress while the BCG is trying to unlock. Please don't misconstrue what I am saying. The lug issue has been addressed by Barrett, LMT, and LWRC with their "enhanced" bolts that have stronger lugs. I've never heard of anyone busting off a barrel extension lug. It's just something to keep in mind. As far as the Adams Arms spring, I have it installed on my AA gun because the manufacturer recommends it. As hard as a short stroke piston system hits the carrier, I'm not sure the spring can expand that quickly to make a difference. Maybe someone from AA can chime in. My guess is they wouldn't include it if it didn't help somewhat but you never know.

I got the AA Xtreme Low Profile gas block for use with a rail. I don't like that you have to remove the rail to service the piston but my LWRC has the same issue. With the Barrett and POF, when you remove the gas plug, the piston components fall out of the front of the gas block for cleaning. The sucky thing about the Barrett is it uses a proprietary barrel with a non standard gas port location. So basically you are stuck with the stock barrel unless you buy an undrilled replacement barrel. The AA, Barrett and LWRC utilize a spring to assure the piston end of the op rod doesn't over travel and fall out of the gas block. POF has a long enough gas block that the piston rod stays inside it even when the carrier is locked to the rear so it doesn't need a spring. However, you can hear the op rod sliding back and forth in the gun when the carrier is locked back. Barrett and AA have the fewest parts: one piece carrier with one piece piston/op rod with spring. The Barrett piston looks like a miniature AK piston. The Barrett gas block has AK style flutes inside and a spot that scrapes carbon off the piston.



This is one of the reasons I've sold some of my piston guns: serviceability. DI parts are plentiful and cheap.

 

So some one shooting them self in the face is a direct result of a di gun and wouldnt have happened if it was a piston setup. Personaly I'd blame it on improper muzzle control.

I also run a free float tube to minimize external forces on the barrel.  I woulnt want to run a system that applies force to the barrel.  I dont ever plan on doing commando training or abusing / neglecting it to the point that it wont function.

Many advantages to a piston

Less oil needed
parts stay cooler and less dirty
more direct force and is much better for SBRs
less gas in your face when suppressed
just as accurate as a DI
don't have to worry about water in the gas tube if you're in the water
overall more reliable

only down side are the proprietary parts and slightly heavier
also a little more felt recoil but that's why it cycles more reliable

edit...who ever tells you that the bolt doesn't run cleaner or just slightly cleaner doesn't know what he is talking about. It is night and day difference and you will not need nearly as much oil. Get a quality piston AR like Sig516 and its a better weapon than any of the DI. If you're going SBR or suppressed than a piston is a must imo. I'd take a SIG/POF/CMMG/HK/LWRC or any other quality piston over any DI AR any day.

I would say that if you're going to shoot a lot of rounds through it, not oil it or clean it, have a SBR and want to go suppressed my choice is the piston. I use a heavier buffer that decreases the cycle time and makes the action much smoother.

But do your own test. Clean a factory DI and Piston AR don't put any oil on it and shoot a 1000 rounds through it over a few trips to the range.

Not sure how you came to that conclusion, the article says nothing about the sergeant shooting himself.

You tell me. You originally posted it, and have since went back and edited your original post.

Indeed, it does. I even ran a SCAR 16S with a Surefire FA556-212 and even that, where it was designed for an externalized piston, had a lot of fouling in the upper/carrier. Still ran cool though, which is merely what I was pointing out.

because i can clean my entire BCG with a quarter of a paper towel after 300 rounds.

I do that with DI.

Yep, to correct spelling in the post, not change the content, please share how you arrived at your position the sergeant shot himself?

I do as well with my DI guns, but my bolt carriers are teflon impregnated nickel (Robar NP3).

While I feel the Sig 516 is a fine weapon, it wasn't without some initial issues. And I would agree with about half your assertions regarding external piston setups.Owning and shooting both, I can't accept blanket statements like EP is more reliable than DI. If you aren't going to clean your gun or not use oil for three thousand rounds, then yes, a piston gun will run better dry, but it too will eventually succumb to lack of lubrication.There is no doubt the bolt carrier is going to stay much, much cleaner with an EP setup. However, the bolt lugs will eventually foul and the piston will eventually require servicing. Also, as I stated above, the assertion that EP's run cooler is wildly overstated. We are only talking a few degrees here.

I enjoy both my external piston and DI guns. They both have their pro's and con's. Seems like there is slightly more koolaid to be had on the external piston side of things for whatever reason so don't take my comments about DI guns as me beating the drum for either platform. But please be realistic. I have yet to find the holy grail of semi-auto rifles, EP or DI. I read your assertion about a DI gun that has had a 1000 rounds put through but how about a DI gun that has 40000 rounds through it without cleaning. Of course it was generously lubed.

http://www.ar15.com/forums/t_2_138/196990_.html&page=1

And of course the carbon is massively built up. It wouldn't be as bad in a piston gun but perhaps the carbon doesn't matter as much as you think as long as it is lubricated.

That line came form your post.

In your own post , right above the link.

I see nothing indicating or implying the mention of a self inflicted wound. I agree, how did you come to that conclusion?

This ^^^^^^^