Pushrod or Impingement?

[Duman]

Do you guys have a preference between piston/pushrod or direct impingement on your ARs?

All mine are impingement, but the LMT pushrod looks attractive. Think I'll buy her a beer....

Your thoughts?

[Great-Kazoo]

You mean Gas Piston? IF you're going to run a can, go piston. If not say the $300 invest in ammo and or training. I have both, mostly piston. The spouses AR is DI as use of a suppressor on her's will be minimal / time of need.

[Hoser]

I have shots lots of gas guns full and semi auto, suppressed and unsuppressed. Its no big deal.

Get a piston gun if you want something different. Just remember piston parts are proprietary and not standardized like gas guns.

[Mick-Boy]

Here's something I wrote up a couple of years ago regarding my experience with LWRC specifically but dealing with piston guns in general.

https://www.ar-15.co/threads/62804-LWRC-or-How-I-learned-to-stop-worrying-and-shoot-DI-guns

[68Charger]

An engineer's perspective- the AR platform was designed for DI (Impingement).. the BCG was never designed for the tilting forces that come from piston driven..

does it work? yeah- there is always leeway in every engineering design. but would it work better if there was more surface area to prevent the BCG from tilting? absolutely!

look at the AK Bolt carrier design as compared to to the AR... the receiver rides in a slot within the Bolt carrier, with lots of surface area.
The downside to DI? Dirty ammo is one example- suppression is also outside Stoner's original design- both suppression and piston driven are outside original design.

The ways they are outside the design are complementary- DI tends to drive out lube- gas-piston does not... so suppression favors gas-piston, but you have to watch the gas pressure of the design- if you want to run suppressed, then you should to get a gas piston system designed for higher gas pressures that come with suppressed.

All this to say- work with whomever you are buying it from, or engineer it yourself... there are LOTS of variables.

[Duman]

Cool....good info, thanks!

[275RLTW]

Look at Primary Weapon Systems long stroke piston system. I've run one for about 60K rounds without issues.

[MarkCO]

No benefits to piston ARs, some draw backs. Even suppressed, I prefer DI. John Noveske preferred DI guns and his reasons are in a few articles.

If you set up the system correctly, the operational window can be moved mitigating the minor issues with DI guns suppressed.

[ray1970]

No benefits to piston ARs

Sure there is. The bolt and bolt carrier stay very clean. So, if bolt cleanliness is high on a guy's list of priorities that might be the way to go.

Fortunately for for me, I don't care much about that and the DI system works just fine as it was originally designed.

[MarkCO]

With a properly tuned DI system, my carriers stay very clean as well...

[ray1970]

With a properly tuned DI system, my carriers stay very clean as well...

Well, no matter how "properly tuned" mine are powder residue still seems to find its way in there. Almost like it's just part of the way a DI system is supposed to function. Go figure.

[MarkCO]

Yes, they are going to get a bit more fouling than a piston. I found a little faster powder to make sure that the powder is all burned before it gets to the gas port helps a good deal. Use slow powder like Varget, it will be a mess.

[ray1970]

Yes, they are going to get a bit more fouling than a piston. I found a little faster powder to make sure that the powder is all burned before it gets to the gas port helps a good deal. Use slow powder like Varget, it will be a mess.

I agree. Choosing the right powder probably makes the biggest difference in how clean the DI system runs. Personally, I've had good results with H335. Admittedly, I haven't tried everything out there. Is there one you prefer that runs really clean?

[275RLTW]

With a properly tuned DI system, my carriers stay very clean as well...

my "off the shelf" pistons do that with any ammo or powder...

[MarkCO]

X-Terminator and AA1680.

[BPTactical]

If the AR was supposed to have a piston, Stoner would have designed it as such. He did design a piston rifle the AR 18 which actually is a great little rifle.

To me, the piston is a hardware fix for a software problem. The biggest selling point is a cleaner bolt/carrier.
Face it, how many really enjoy cleaning a nasty bolt and carrier?

IMO a piston adds components that can fail/malfunction, mechanical complexity, weight forward on a barrel and cost.
Parts left off cost nothing, parts left off cannot fail.

[ray1970]

Face it, how many really enjoy cleaning a nasty bolt and carrier?


[pick-me]

Maybe I'm just a bit masochistic.

[earplug]

Using the few powders and bullet combinations I have used as a comparison, I'd say the issue was very small. Powders have more effect then operating system.

[Great-Kazoo]

[pick-me]

Maybe I'm just a bit masocheesit.

[BPTactical]

I see what you did there.....

[ray1970]

Hey, it ain't easy being cheesy. [Coffee]