Brownells Gun Techs Steve Ostrem and @CalebSavant are back to take on the myth that piston-operated AR-15s are better / more reliable than standard direct-impingement ARs. As the guys demonstrated in an earlier Smyth Busters episode (“Is the AR-15 Really Piston Operated?”), the AR-15 is not actually a pure direct impingement rifle but a kind of hybrid, with the bolt operating like a piston. In this episode, “direct-impingement” means an AR-15 with the traditional gas tube above the barrel.
Caleb points out there have been a lot of attempts at piston-driven AR-15s, some of which were terrible. The Heckler & Koch HK416 was purpose-designed to be piston-operated, and it works VERY well, as does the Brownells BRN-4. Any good piston-operated AR-15 style rifle will be more expensive than a direct impingement one because it just costs more to manufacture the additional moving parts. And it is heavier.
So what’s the benefit of a piston? A piston AR runs CLEANER and COOLER. It doesn’t blast hot gas back into the receiver and bolt-carrier group, which increases the gun’s longevity. This is a huge benefit in full-auto fire, too. A direct impingement AR-15 runs hotter and dirtier, but the rifle is lighter. And after 60+ years of development and refinement, it is also very reliable.
What about those “plug-n-play” piston conversion kits? They involve engineering compromises that cause “bolt tilt.” In direct-impingement, the gas pushes on the bolt in line with the bore so the bolt and carrier move in a straight line. With a piston conversion, the force hits a lug on top of the carrier where the gas key would be. This force is off-center, causing the carrier to tip down at the rear, tilting the bolt upward. The result is accelerated bolt wear and malfunctions. Purpose-built piston guns like the HK416, BRN-4, and AK series are designed to keep the piston force properly centered.
So the myth is BUSTED. A piston AR is not always better than a direct impingement AR-15. Direct impingement is more reliable than a piston conversion kit. But a purposed-designed piston system is more reliable than either of them. A direct impingement AR-15 is the most cost-effective option for sport shooters. But if you have the spondulicks, try the HK416 / BRN-4 route.
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A good DI system is better than a converted piston system! Also, it's January! That means it's time to vote for me in this years Gundie Awards as "Most Dapper"!
how would you overheat your receiver without melting the barrel first?
So you don’t think the LWRCI piston driven AR is any good???
It’s a solution searching for a problem. Bolt carrier on an AR are floating because the force is in the center. Every other non AR piston design uses bolt rails.
Cleaner, cooler, better for suppressors. Seems like if you actually have to use the 2nd amendment for its intended a piston system would be a better weapon… don't get conversion kits, they are prone to tilt and cause malfunctions.
The fewer moving parts, the better…..
Adams arms pistons have always worked for me.
Um,,, no.
Eugene: probably
Superlative Arms piston kit runs like a champ.
I bought a POF and it broke during hard training. Not something I want to bet my life on. I sold it and now I run BCM DIs.
PWS MK116 MOD1
You didn't mention Adcor.
thanks
Piston: more weight, more moving parts, more prone to failure due to more moving parts, can get clogged up and operate at a reduced efficiency, noticeably less accurate.
Direct impingement: gets a little dirtier in the breach area. Most gun owners are lazy as hell and turn their laziness into bragging rights on how long it is been since they have performed any maintenance on their rifle. That's like bragging how long it's been since you have checked or changed the oil in your car, pure stupidity
And the guy next to the cameraman going 3 2 1…drink.😉😄😄
Had a Bushmaster piston kit back when piston kits were the new thing. It ran fine.
There is a company that sells conversion kits (as well as dedicated piston uppers) that has solved the problem with bolt tilt with a new bolt carrier design, and includes the bolt carrier in their conversion kits that are as reliable as the dedicated uppers.
Sig Spear lt for me.
Love my HK416 and my newly built BRN4 great video as always
I suppose most people who think of a piston system think of an AK, and assume it's automatically more reliable.
I would like to say a piston ar also has more moving parts. Which in turns means more parts to break. Some of us keep spare parts for our Di guns. Do you keep spare parts for your piston Gun?
DI gets complicated though when you're talking reliability with suppressors. This seems to be the only reason to consider a piston system with adjustable gas system. Otherwise, stick with DI, much lighter, much accurate, much better.
Well. I’ll take a Pws or Lwrc over a cheap ass di model any day of the week.
What do you think of the stag arms model 15 piston rifle?
Totally agree!
Years ago, I purchased a CMMG piston system from Brownells. I installed it on 11.5 SBR Bushmaster with a LaRue handguard. I drilled and pined the gas block and had to mill the inside of the LaRue so it could fit. I put tens of thousands of rounds through it at action Rifle and three-gun matches. I did purchase Two more of the CMMG systems from Brownells and have had no issue with them (lower round count). I notice a different recoil impulse to add to the differences. My two cents. Keep up the interesting videos.
What about Adams arms piston guns?
In my experience. Piston guns, recoil a bit more, then their DI counter parts, as well. Nothing unmanageable. But it's a thing. Thanks for the share!!
How reliable is the piston system on the LWRC? How does a piston do with suppressors?
Holy shit. 1. Hk416 isn’t that great. Its over priced over gassed and is all proprietary. And apparently needs to have its piston cleaned? Lwrc is self cleaning and not completely proprietary. Also is gassed correctly
2. “It runs cleaner” lolololol put a suppressor on it and see how clean it is.
3. “It runs cooler” oh my God i used to think you two clowns knew what you were talking about.
Tldr pistons are shit and an old operating system. Siphoning gas to operate an internal piston is the modern way.
UNSUBSCRIBED.
Thanks Gentlemen, awesome segment!
Good video
That Caleb knows his stuff.
Yes if they are implemented and adjusted better. No if the opposite.
If piston driven AR type guns are so lame, why did anyone take the time to make them ?
More reliable…more balanced…..quieter….I'd say definitely.
California going electric without the infrastructure.
Climate Change the tundra melt
Russia will be drilling for oil all day long.
White man speak with fork tongue
Stag Model 8 piston still going strong.
All metal gas block and stainless steel rod.
Quality product
2010 wants their arguments back.
Back when I was imagining building a rifle I thought for sure that piston was the way to go. It seemed so obvious! After learning a bit more about how the AR platform runs, and hearing about how the piston-rod-driven bolt carriers sometimes can't take the impact after a while, it became clear what the benefits of having the piston inside the BCG are. You're directly driving the bolt carrier back with the gas expanding inside of it, and it unlocks and yanks the bolt back with it. That's a system that involves much more mass whose inertia must be overcome which means it can run a bit smoother IMO. I'm no expert, these are just the thoughts of a total novice.