Advantages of Piston AR's?

  by David Merrill, MilCopp Tactical  


Let’s talk frankly about advantages and disadvantages of piston-driven AR-15’s. Do they help prevent horrible malfunctions? Do they increase reliability? Is the gas system really a problem to begin with? There’s a lot of hyperbole and exaggeration on the subject all over the internet but let’s actually take a critical look at the system for a change:

If we want to discuss why AR's actually malfunction, this seems to be the thread to do it in. If you have a properly built/assembled AR, malfunctions can typically broken down into MEAL:

MEAL means:
(notice that, "craps where it eats!!$#$%%^" isn't on the list ;) )

M: No mag-fed rifle, no matter how expensive or robustly built, will feed from a crappy magazine.
E: Same for a bad/worn/weak extractor.
A: Ammunition has the same pitfalls. Yes indeed, some rifles will eat the cheap stuff more but that's usually based around the extractor and the existence of a chrome-lined chamber (chrome is slippery and allows for better feeding/extraction/resistance to carbon buildup). Very out of spec ammo won't work well in anything.
L: The singular point *may* be lubrication but it's really a non-issue as on a standard AR. Some lubrication may need to be added (as outlined in the AR-15 Maintenance article). It is unlikely that you will go through several hundred rounds and not have the opportunity to add lubricant someplace along the way. I've been in some big fire fights (Operation Phantom Fury: Nov 04' invasion of Fallujah) and I never spent close to 600 rounds in a single sitting.

However, if you're terribly worried about lubrication (which you shouldn't be unless you run a lot of FA/suppressed/SBR or combination thereof), a FailZero BCG upgrade solves all of the problems that a piston "fixes" without any of the downsides.

I routinely run my SBR both FA and suppressed and out of shear neglect, tend not to clean
until above 2k rounds (and that is with zero lubricant!). It has reached the 2k mark without cleaning or lube three times now. I honestly always intended to clean it every 1k but forget or whatever.

It's really a niche product but if it helps you sleep better at night...

Here's a very good article by Mike Pannone (If you don't know who he is or his background, just google him.)

The negatives of gas piston AR's are many:
-Firstly, there is no standard right now. Every company seems to make their own. This means that when something breaks, good luck finding spare parts for it--anywhere. Furthermore, not all of them are created equal.
-Carrier tilt (more present on some designs than others but it still persists as a problem; there's a reason why from-the-ground-up piston guns have a stacked carrier arrangement as opposed to a linear one)
-Uses very violent action to unlock the bolt, unlike the linear action of DGI (I suppose this might fall under 'Carrier Tilt' but I thought it was worth mentioning separately).
-Increased weight
-Decreased accuracy (in many cases)
-Doesn't improve anything from
MEAL, as outlined above, except in specific niche cases, where better solutions exist.

Many of the piston guns that have good track records (LWRCi, for example) could likely do just as well with a DGI rifle because they put together quality rifles to begin with--regardless of the gas
system used. I have zero problems with from-the-ground piston guns. My FN Scar is my second favorite rifle currently in my collection (#1 belongs to my 11.5"
BCM SBR). The AR is a great system--we already have plenty of snake oil marketed towards us without people buying into more of it based on, "it craps where it eats!!!@!#@#". I can't help but think the mythos surrounding the Kalash' has helped further this fad in marketing.

It is noteworthy that I have a high speed associate who brought an LWRCi shorty upper with him to
Afghanistan last year. When he got back, I asked him how it ran for him. He said, "It ran good--no problems" but when I asked him how the CQBR's ran (10.3" barreled Crane DGI shorties) he said, "they also ran really good. I'm not bringing the LWRCi next time."

Anecdote I know but telling nonetheless.