AR15's - direct impingement vs gas piston

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C172 Heavy
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Re: AR15's - direct impingement vs gas piston

#16

Post by C172 Heavy »

I've been running an Osprey kit on my gun since 2010. Gun started as a 16" carbine. It was a learning experience. I was using a Yankee Hill clamp on gas block/sight and the bolt carrier moving back into battery would cause the OP rod to impact the front gas port receptacle and slowly drive the gas block forward until the gas port was no longer inline with the gas port on the gas block. Tried a bunch of things to correct this but nothing ever really worked. I then SBR'd the rifle, went with a 11.5" Adams Arms Voodoo barrel, and both dimpled and cross pinned the Badger Ordnance gas block. I also went with a PWS enhanced buffer tube that was designed to alleviate carrier tilt issues (never saw any indications of that problem prior but felt better doing it). I've since run thousands of rounds through the gun (mainly suppressed) and have had zero issues. I was my own guinea pig and spent a lot of time trying to figure stuff out. I run the bolt without gas rings, standard buffer spring, and a carbine buffer packed full of tungsten powder (was too cheap to buy a H3 and now too lazy to fix what's not broke). I have become a firm believer in Salt Bath Nitriding, neither the barrel nor Osprey kit show any wear consummate with having seen close to probably 8,000 rounds.


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Re: AR15's - direct impingement vs gas piston

#17

Post by Jack Dupp »

So what suppresses better as far as sound to both the shooter and a bystander? True piston like the PWS or 'direct impingement' internal piston like a standard AR15?
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Re: AR15's - direct impingement vs gas piston

#18

Post by C172 Heavy »

I don't know that I've ever been able to tell the difference sound wise. I can definitely tell by either gas in the face while shooting or observing the ejection port. It get's pretty gassy on a DI with can. Now, my buddy set up his DI gun to run only suppressed and after a lot of trial and error he got the rifle set up to run 100%. It runs on a very small gas port delivering minimal gas with a weird buffer/spring setup and only on like one factory loading or his handloads. He's running a 12.5" versus my 11.5" and a an AAC can versus my YHM. I can't tell a difference.
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Re: AR15's - direct impingement vs gas piston

#19

Post by YNOTAZ »

This is a good Vid where DI v Piston is just one consideration when looking at weight v. functionality. He also mentions all the folks that have tested the difference and where one is preferable over the other.

He discusses piston v. DI at 11 minutes in, but the entire vid is worth watching.

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Re: AR15's - direct impingement vs gas piston

#20

Post by Jack Dupp »

C172 Heavy wrote: February 23rd, 2023, 7:49 am I don't know that I've ever been able to tell the difference sound wise. I can definitely tell by either gas in the face while shooting or observing the ejection port. It get's pretty gassy on a DI with can. Now, my buddy set up his DI gun to run only suppressed and after a lot of trial and error he got the rifle set up to run 100%. It runs on a very small gas port delivering minimal gas with a weird buffer/spring setup and only on like one factory loading or his handloads. He's running a 12.5" versus my 11.5" and a an AAC can versus my YHM. I can't tell a difference.
Thanks for that. I've never messed with piston ARs, but like your buddy, I had to mess with my 16" middy a lot to get it where I'm happy. I was getting gassed out bad. I ended up using an adjustable gas block virtually closed all the way, a side charging upper, and a 9mm buffer to get a pleasant shooting gun suppressed. It sounds great and has almost completely eliminated gas to face, but now it only runs with the can attached. Take the can off and it's a single shot repeater.

If I can get reliable function without gasface (while keeping the same sound suppression) with a piston upper, then that would be a total winner. Unless shooting precision went to crap with the piston...
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Re: AR15's - direct impingement vs gas piston

#21

Post by campinginaz »

C172 Heavy wrote: February 22nd, 2023, 8:59 pm I've been running an Osprey kit on my gun since 2010. Gun started as a 16" carbine. It was a learning experience. I was using a Yankee Hill clamp on gas block/sight and the bolt carrier moving back into battery would cause the OP rod to impact the front gas port receptacle and slowly drive the gas block forward until the gas port was no longer inline with the gas port on the gas block. Tried a bunch of things to correct this but nothing ever really worked. I then SBR'd the rifle, went with a 11.5" Adams Arms Voodoo barrel, and both dimpled and cross pinned the Badger Ordnance gas block. I also went with a PWS enhanced buffer tube that was designed to alleviate carrier tilt issues (never saw any indications of that problem prior but felt better doing it). I've since run thousands of rounds through the gun (mainly suppressed) and have had zero issues. I was my own guinea pig and spent a lot of time trying to figure stuff out. I run the bolt without gas rings, standard buffer spring, and a carbine buffer packed full of tungsten powder (was too cheap to buy a H3 and now too lazy to fix what's not broke). I have become a firm believer in Salt Bath Nitriding, neither the barrel nor Osprey kit show any wear consummate with having seen close to probably 8,000 rounds.
That is a lot of rounds! Thank you for the reply! I've also recently thought of doing an AR based SBR so I can swap uppers etc. Good to know the shorter piston uppers work well!
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Re: AR15's - direct impingement vs gas piston

#22

Post by campinginaz »

YNOTAZ wrote: February 23rd, 2023, 8:16 am This is a good Vid where DI v Piston is just one consideration when looking at weight v. functionality. He also mentions all the folks that have tested the difference and where one is preferable over the other.

He discusses piston v. DI at 11 minutes in, but the entire vid is worth watching.

Pretty good video for sure! I don't know if I agree with everything but there is a lot to consider here. I'm also going to look into the iron sights he had on there!
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Re: AR15's - direct impingement vs gas piston

#23

Post by C172 Heavy »

Jack Dupp wrote: February 23rd, 2023, 8:49 am If I can get reliable function without gasface (while keeping the same sound suppression) with a piston upper, then that would be a total winner. Unless shooting precision went to crap with the piston...
I did not notice any accuracy issue with either the original 16" or 11.5" barrel out to 300 yards. Didn't spend any time shooting further as I used my MK12 clone for that. Now that you have me thinking about it I might see if Osprey has a 308 kit that I could use on my upcoming build. An 18" SPR style build. That would be a good test of accuracy.
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Re: AR15's - direct impingement vs gas piston

#24

Post by QuangTri »

Suck My Glock wrote: February 21st, 2023, 9:45 am And on larger calibers in AR10 types, the difference is even less noticeable.
I know POF makes or made a completer piston AR10 rifle.

Never seen a piston kit for the big block AR, might be in the market for one if Adams or other solid company makes one.
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Re: AR15's - direct impingement vs gas piston

#25

Post by xerts1191 »

campinginaz , give us a range report and your experience shooting the newly acquired piston upper
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Re: AR15's - direct impingement vs gas piston

#26

Post by campinginaz »

xerts1191 wrote: May 1st, 2023, 8:20 pm campinginaz , give us a range report and your experience shooting the newly acquired piston upper
Haven't shot this one yet, but hopefully in the next few weeks.
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Re: AR15's - direct impingement vs gas piston

#27

Post by mock0013 »

If you are going to shoot a DI suppressed get a Radian Raptor SD charging handle
Image
Notice the ports to dump into the bolt area and it has a lip on the end of the charging handle to direct gas up and away from directly back in your face.

Not all piston guns make great suppression hosts as I have Sig 556R piston gun that has a small break between the upper and lower where gas destroys the shooter in like 2 shots.. It's brutal.. your eyes hurt and water and you can't see for a few seconds if you rapid fire past 2 shots. Sig doesn't have (anymore) an adjustable gas system to reduce the pressure for suppressed sadly.
Piston systems are typically about 1/2lb heavier out in front of the gun.

I have a 2a Armament DI AR15 5.0lb factory built with every accessory they make and it shoots so soft and
My CMMG 10" AK47 is piston and shoots crazy soft.

the other nice thing about piston guns is the stock folds and when shooting suppressed you don't have to deal with Buffer weight replacements and springs.. the piston systems typically can shoot a broader range of ammo automatically which I value instead of having to jack with it.

B&T Piston and Scar16/17 piston setups are excellent. I understand the Sig MCX is also softshooting as is the MPX.

If you are installing an adjustable gas block on AR make sure to install with Rockset or Loctite Red and give it a good 24hrs to setup to minimize the gas blocks coming loose while shooting. You get what you pay for with Gas blocks on DI so don't cheap out if you plan to use a can and adjust it a lot or shoot lots of ammo.
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Re: AR15's - direct impingement vs gas piston

#28

Post by BigNate »

campinginaz wrote: February 20th, 2023, 8:26 am I'd like to know if any of you have gas piston AR's and do you like them more than traditional direct impingement. There are so many brands out there now and I'd love to know more from you guys.
I have one gas piston AR (stock Sig 516 Patrol) and I like it plenty. That said - I don't know that there is a ton of value in going that direction unless you plan to shoot suppressed. My understanding has always been that gas piston is "better" in two situations:
1) When shooting suppressed - where the suppressor changes the pressure map for gasses at the gas port on a DI gun causing you to get a bunch more gas / carbon back through the gas tube and out the ejection port, and accelerating the rate at which the gun gets carbon clogged.
2) When shooting very large numbers of rounds between cleaning... like VERY large numbers of rounds... thousands... and the carbon buildup around the bolt and in the receiver can eventually start to impact function.

I think that #1 is reasonably well established as fact - and can be observed pretty easily by putting a suppressor on the gun and shooting into the wind to see how much difference there is (and it will no doubt vary by gun and suppressor so YMMV).

#2 is probably a non-factor for just about every civilian shooter - in that you probably are not going to be in a situation where you "need" to shoot thousands of rounds between cleanings and if the gun malfunctions it could cost you your life. If you never clean your guns - expect them to eventually have issues as a function of carbon buildup and grit in the works. Do DI guns get more carbon into the the BCG and receiver? Yep. Does the incidence of malfunction as a function of this carbon exceed the incidence of malfunction in a similar gas piston weapon used / neglected the same way? Who knows. Is the concern about a carbon clogged DI gun causing malfunctions very easily avoidable simply by cleaning the gun every once in a while? Yep.

For my part - if I were building a gun that I intended to shoot suppressed (and I am) - I'd build / buy a quality gas piston gun - primarily to avoid the extra gas in the face from the ejection port... Otherwise I'm not sure that the extra expense is warranted.

My 2 cents.
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Re: AR15's - direct impingement vs gas piston

#29

Post by campinginaz »

Great advice on shooting suppressed. I don't have a 5.56 suppressor and probably won't get one. I definitely like the fact that they run cleaner, less to clean and more reliable. My PWS has been awesome, just haven't shot the Adams Arms yet. A few people on here have said the Adams Arms are pretty good, and honestly they aren't much more than a direct impingement.
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Re: AR15's - direct impingement vs gas piston

#30

Post by QuietM4 »

If God had wanted the AR-15 to be a piston gun, He would have told Eugene Stoner to do it that way.
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