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Piston vs Direct Gas Accuracy Test

This is a discussion on Piston vs Direct Gas Accuracy Test within the M16 AR15 forums, part of the Rifle Forum category; Article from NRA's Shooting Sports Magazine about accuracy test of piston AR vs direct gas AR: https://www.ssusa.org/articles/2017/..._campaign=0317...


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Old March 1st, 2017, 12:43 PM   #1
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Piston vs Direct Gas Accuracy Test

Article from NRA's Shooting Sports Magazine about accuracy test of piston AR vs direct gas AR:

https://www.ssusa.org/articles/2017/..._campaign=0317

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Old March 1st, 2017, 01:51 PM   #2
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Interesting article, thanks for taking the time to post it up for us.

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Old March 2nd, 2017, 04:54 AM   #3
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Back in the 80s & 90s I built pistons and bolt carrier keys for Walt Langendorfer's Rhino System.

Dane

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Old March 2nd, 2017, 09:40 AM   #4
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I have owned, built and shot several dozens of AR 15 and AR 10 rifles, all with DIRECT gas impingement.

The AR 10 rifles are, ON AVERAGE, the most accurate semi auto .308/7.62 NATO rifles I have personally shot, with many of them shooting well under MOA with ammo that they like. Personal best is 5/8" five shot @ 100 yds from one of my DPMS LR308B rifles. The very nice 2.5 lb trigger I installed probably helped.

The AR 15s I have shot do not seem to be as accurate, ON AVERAGE, as the larger caliber AR 10s ...
for no particular reason I can discover. Most of my AR 15s were 2 MOA rifles, with a few MOA, and even fewer SUB-MOA. One of my target AR 15 builds, using OGW parts, a FLUTED SS HBAR, and a SET trigger, would shoot one hole at 100, with the right ammo, but such OUTSTANDING performance was very rare.

I have fired tens of thousands of rounds through forty or so AR 10 rifles, mostly the ORIGINAL AR 10 MILSPEC models, Sudanese and Portuguese, and these were some of the most reliable semi auto rifles I have used. The larger tolerances, more powerful ammunition, and heavier components, made these GENUINE AR 10s perform well. I can not remember any failures to feed due to carbon build up, and no durability issues [ although I did have to repair the back of the mag well in one Sudanes AR 10, which had been dry fired too many times without a bolt carrier installed]. The original ultralight aluminum WAFFLE magazines were a bit fragile, and they can cause feed issues, but the modern MAGPUL Pmags are about as reliable as you can get.

The MODERN AR 10 /AR 15 HYBRID CLONES, which use as many AR 15 parts as possible, do not have as good a reputation for reliability or durability as the old originals. However, once I scrapped the metal DPMS magazines in favor of the Pmags, reliability increased significantly. Unfortunately, my DPMS built LR308B had the shorter CARBINE length gas take off location, and it was OVERGASSED, and tended to be a bit fussy with some ammo.

Here in Canada, here has been a resurgence of interest in the ORIGINAL AR 10 rifle design, as THEORETICALLY, it would NOT be restricted by Canadian law, as are all AR 15s, and derivatives thereoff. However, since the AR 15 is a derivative of the AR 10, there is some legal argument that since the AR 10 CAME FIRST, it is NOT covered by Canadian Restricted definition regarding AR 15s and derivatives. So an original AR 10 design, which does NOT contain too many AR 15 parts, may slip between the cracks and be NOT RESTRICTED.

So far, I seem to achieve the accuracy/reliability/durability balance from all my AR designs without resorting to the more complicated piston designs.
And so far, I have not seen any piston ARs that provide a SIGNIFICANT improvement,
so for me,
the good ol'
K.I.S.S. and "Parts left out rarely break or fall off" design philosophies of the the orifinal IMPINGEMENT designs,
seem good enough for me.
AS ALWAYS,
YPMMV
(;-[)

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Old March 2nd, 2017, 12:33 PM   #5
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Most of reliability of the original AR-10s is due to the efforts of Artillerie Inrichtingen.

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Old March 2nd, 2017, 04:37 PM   #6
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The thing that I like most about piston system ARs is the platform isn't exhausting soot and gasses five inches from my air intake.

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Old March 2nd, 2017, 05:21 PM   #7
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Don't know what AR15's you have been shooting Laz, but it is a rare AR15 that I build and shoot that will not shoot sub MOA.

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Old March 2nd, 2017, 05:26 PM   #8
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Quote:
Originally Posted by MD66948 View Post
Back in the 80s & 90s I built pistons and bolt carrier keys for Walt Langendorfer's Rhino System.

Dane
I bet most guys on this forum never heard of the Rhino system. I remember them from 1980s. Guns and Ammo did an article on them in the Proof House section in the December 1985 issue. It is a positive article. Complete upper was $180.00. It was far ahead of its time.

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Old March 3rd, 2017, 02:39 AM   #9
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I don't have a gas piston AR15. Got a gas pistol SIG 556R and man does that thing stay clean inside compared to the DI AR15's. The AR15's need to have all the crud cleaned out and be relubed after each range session (to keep my conscience clear if nothing else) and the 556R can use the same smears of grease on the bolt for a year or more before I feel the need to wipe off the still green looking grease and apply new grease.

As to the gas piston affecting the accuracy? I really have to wonder about that.

Does the gas piston start moving while the bullet is still in the barrel? Hard to believe, if someone says that.

Does the bolt lock up in the barrel differently due to the gas piston system bolted to the front area of the barrel? Again, hard to believe the headspace or the angle of the bolt face, etc. is different due to something bolted to the barrel that isn't touching the bolt when the rifle is fired.

Does something in the gas piston system move when the trigger is pulled or the hammer is falling? Again, I'd find that hard to believe.

People that owned the SIG 516's loved them, both the reliability and accuracy. I used to think about buying one but SIG has soured me on their customer loyalty/support, so that's out.

I can see a different rifle with a different barrel "liking" different ammo than another rifle. Maybe the test should have included a search for ammo that shot better in the gas piston rifle. That's one reason I piddle with my rifles/reloading so much. I'll be darned if I'm going to fiddle around with a rifle that needs a special load to shoot well. If an AR15 doesn't shoot the same loads well that my other AR15's shoot it's going to be a gift to a relative or I'm getting rid of it. Don't think poorly of me for giving away rifles I don't care for. Sometimes it's the other way around. The most accurate 20" AR15 I've ever shot now resides in the safe at my oldest son's house.

I'm just saying, taking two rifles out and shooting groups with them and saying one system is better than another, without some extensive testing/troubleshooting/ammo variety, etc. isn't a real good test.

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Old March 3rd, 2017, 02:49 AM   #10
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Old March 3rd, 2017, 04:44 AM   #11
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Quote:
Originally Posted by RDS View Post
I bet most guys on this forum never heard of the Rhino system. I remember them from 1980s. Guns and Ammo did an article on them in the Proof House section in the December 1985 issue. It is a positive article. Complete upper was $180.00. It was far ahead of its time.

Sad to say but when Walt retired and had his shop cleaned out by a friend of mine 5,000 Rhino Devices were thrown out into a dumpster. My friend cleaned out the whole shop. He did some areas that he was not suppose to do.

https://en.wikipedia.org/wiki/Walt_Langendorfer

Here is a correction I made in the PA Firearms Owners Forum to someone's post about Walt:

http://forum.pafoa.org/showthread.ph...t=rhino+device

Dane

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Old March 5th, 2017, 05:43 PM   #12
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I just literally got sick. I'd kill for a Rhino device. My friend Karl had one on the only AR he had.

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Old March 26th, 2017, 03:38 PM   #13
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Interesting tests. I will say it's cool to see how different folks approach the problem of converting a DI platform to piston. I'd like to see something like a comparison between a PWS (long stroke piston) and a DI gun build from PWS/Bootleg guts or LWRC short stroke vs. LWRC DI to get an apples to apples view.

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