Thoughts on Piston Driven AR's

[Dagga Boy]

Jay Cunningham is right on the money. I get asked this all the time. My response is usually that there are a couple of hundred guys in the US military that "need" a piston gun, and they have them.

I have run my DI AR's in head to head very high round counts against piston guns without issue. In the most notable case, a Ken Elmore built Colt L/E 6920 ran 1920 rounds shot as fast as the users could pull the trigger (64 shooters hand the gun off) while doing an Aimpoint demo. This was run next to an HK416. The only difference was that my gun was hot around the barrel, and the HK wasn't. Other than that, neither gun had a malfunction or issue. The reality, is most of will never have 64 guys from one of the premier SWAT teams in the country lined up with a 30 round magazine in hand to burn through their gun (most of the internet genius's will never shoot this many rounds in the life of their gun). I do stuff like this regularly, and all with DI guns. I am currently using Centurion Arms guns with a CHF barrel that has the MG chrome lining and are mid length gas systems for my demo guns. My previous LMT MRP demo gun has 30,000 rounds of very abusive use and is rarely cleaned and has never had any major issues. Again......I need a piston because....? The key to running a DI gun, is running a top tier AR and stay away from hobby guns.

I do love my Steyr AUGs, so I have piston guns if I need them.

[jslaker]

They certainly could be having problems when making an extreme temperature switch. There are all sorts of firearms that do not work as well at extremely cold temperatures, and going from warm to extremely cold only serves to amplify those effects. AI goes so far as to develop a special purpose sniper rifle for artic/cold weather environments due to effects it has on a bolt action rifle. It would stand to reason that the piston guns could suffer from some of the same issues. The DI guns don't work so great when it is cold either. I wouldn't attribute cold weather issues solely to one make and model.

Absolutely. I meant it more as a "hey, this is an interesting example that all guns can be tripped up" as much as anything. From what I understand, a lot of the griping amongst the Norwegians apparently stemmed from the fact that they generally didn't run into those issues as often with their old G3s.

I did a bit more digging after posting, and, lo and behold, it looks like they also had similar problems with some of their DI C8s.

[45R]

I've had both DI and Piston AR uppers. I kept my DI and have sold my Piston rifle. I saw no added benefit to my piston rifle other than it shot a bit cleaner.

[P30shtr]

Jay Cunningham is right on the money. I get asked this all the time. My response is usually that there are a couple of hundred guys in the US military that "need" a piston gun, and they have them.

The only difference was that my gun was hot around the barrel, and the HK wasn't.
.

C'mon, nobody wants to get "burned"

[DocGKR]

While initially excited by the piston concept, over the last 5 years, I have come to the conclusion that 90% of users will be better off with a quality 16" mid-length DI AR15. In addition to Colt, DI rifles by BCM, Centurion, DD, KAC, LaRue, as well as LMT and Noveske (those w/a true 5.56 mm chamber) all run well. The highly esteemed, extremely experienced Pat McNamara recently mentioned that he prefers a 5.56 mm DI 16” barrel AR15 with a long FF rail and a RDS (w/flip up 3x magnifier as a useful addition) for the majority of his carbine use, including indoors for CQB; he specifically mentioned LaRue and DD AR15’s as working very well for him. Kyle Defoor mentioned nearly the same thing in a recent class. I fully agree with them and run almost all my carbines the same way:

[ADKilla]

While initially excited by the piston concept, over the last 5 years, I have come to the conclusion that 90% of users will be better off with a quality 16" mid-length DI AR15.

Concur. While the rage now a days is tacti-cool, a good DI AR-15 with a light and a RDS will solve most of your problems. Even when I was in the sand boxes of both Iraq and Afghanistan, my USGI M4 ran fine; and that was a government issued weapon and very fine sand that got into everything. For most civilians who will never see the desert of the Middle East, a quality DI gun like the S&W or Daniel Defense will be fine for you in normal settings.

[will_1400]

I agree with DI being a good system. Granted, my experience with ARs thus far is being issued a beat-up M16A2 during my fam fire/quals at CATM, but considering the only problem I had was my dumb ass accidently grabbing an empty mag during a reload, my experience was positive.

[Failure2Stop]

Concur. While the rage now a days is tacti-cool, a good DI AR-15 with a light and a RDS will solve most of your problems. Even when I was in the sand boxes of both Iraq and Afghanistan, my USGI M4 ran fine; and that was a government issued weapon and very fine sand that got into everything. For most civilians who will never see the desert of the Middle East, a quality DI gun like the S&W or Daniel Defense will be fine for you in normal settings.

Unless you have a need for instantly changing from suppressed to unsuppressed with a 12.5(-) barrel, a quality DI AR will not only be fine, but wholly acceptable, and in many criteria better.

[jslaker]

Unless you have a need for instantly changing from suppressed to unsuppressed with a 12.5(-) barrel, a quality DI AR will not only be fine, but wholly acceptable, and in many criteria better.

Only other exception I'd throw in would be sustained full-auto fire -- ostensibly the reason for the IAR being based on the HK416 -- but the average shooter doesn't have access to FA lowers, so that's pretty niche as well.

[Failure2Stop]

Only other exception I'd throw in would be sustained full-auto fire -- ostensibly the reason for the IAR being based on the HK416 -- but the average shooter doesn't have access to FA lowers, so that's pretty niche as well.

The fact that two Colt submissions (both DI) made it to the final cut on the IAR selection prettty much killed the argument in my opinion.
Piston systems do not appreciably drop chamber temperature below DI systems, the real cause of cook-offs.
The IAR was chosen due to it's performance in relation to a needs document, not because of its operating system. It is significantly different than an M16/M4 in many more areas than just operating system, and all of those changes contribute to its success where others failed.