Gas vs. Piston

[jasgo]

I was looking to get a new AR. Actually was going to order a Colt 6721 with a heavy barrel. Got persuaded to get a long piston design Mk116 rifle made by PWS (Precision Weapons System) at a favorite gunshop. Handled one and it was also broken down so I could examine the parts. Weighs a little under 7lbs. All makes of two stage triggers are supposed to fit. I won't get mine for 3-4 months so won't know how it will shoot until then. Seems to be a lot of favorable reviews on it.

[DefensiveCarry.com]

[fernset]

Thank you everyone for your input. Muach appreciated.

[pmcjuryny]

I haven't looked at pistons in a little while but I seem to recall that the parts where not always interchangeable. Maybe someone else can say if this is still the case

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[jonconsiglio]

I haven't looked at pistons in a little while but I seem to recall that the parts where not always interchangeable. Maybe someone else can say if this is still the case

Sent from my ADR6350 using Tapatalk 2

You're correct, they are not interchangeable. There's no milspec for them as of now, so each company does it their own way.

[Geronimo45]

Looking to get an AR 15, what should I get. New piston driven or conventional gas driven?
Pros/cons? Pricing? Availability or parts?

I don't have any experience with these but have read the piston driven tend to heat up at the foreend but are easier to keep clean and maintain? Opinions?

Conventional gas system will be cheaper. I wouldn't trust the cheap piston systems. PWS, LWRC, and HK seem to be good choices, but they are expensive.
If you're putting lots of rounds downrange a year (tens of thousands) you might be better off with a piston system. Since the bolt is mostly protected from gases, parts last much longer than direct impingement systems. This matters with high round counts (more parts replaced more often). Short barrels can run better in a piston system than direct impingement. Once you get shorter than 14", problems start to crop op with DI.
DI also heats up under the handguards. If you're firing a long string, you should wear gloves... or use a foregrip.

[jasgo]

Yes, for short barreled AR's, a piston design may have better inherent advantages in terms of reliablity. The carbine versions of the M16/AR15 has the gas bleed closer to the chamber using a short gas tube. The entire recoil/impulse cycle rate is altered from the original barrel/gas bleed length design. For most civilians, probably not a significant factor since usage is a lot different from military applications (i.e. fully automatic firing, continual firing in a firefight). Could be a factor for civilian owners who take intensive rifle courses though.

After experiencing eroded gas rings and a fractured bolt in a DI carbine, I can't wait to see how cool and clean the PWS I'm waiting for will run. I recommend anyone with a DI rifle to have spare gas rings, gas tube, gas tube pin, and bolt carrier group parts.