Got a chance to shoot that gas piston rifle today, WOW!


June 11, 2009, 01:36 AM
I like this rifle.
Advantages, clean, very very very clean, in fact after a few hundred rounds I pulled the bolt carrier while the barrel and gas piston were smoking hot, and the bolt carrier was normal air temperature, and still wet with oil. The only dry spot was the bolt face, also the only dirty spot on the entire bolt assembly. To make this more fun I used very dirty brass rounds, and cleaner hot loaded steel cased rounds. Even the gas piston was not very dirty.
Things I noticed, the recoil feels a bit different, with the piston faced so that the gases are going through the small ports it has a bit stronger recoil than a DI rifle, and its LOUD. With the piston faced to vent gases through the bigger ports the recoil is very very mild (softer than any 16 inch carbine Ive ever fired), but the noise is directed a bit differently and its louder than a DI rifle.
The sights were easy to set, and required very little adjustment, in fact I was zeroed shooting 3 shot groups with 9 total rounds. I fired 3 rounds, made my left and down adjustment, then verified with 2 groups of 3 rounds.
Next I switched to the Bushnell 1X32 T dot reticle MP scope, 6 or so total adustments at 25, 50, and 100 yards, it was set.
Firing rapid this rifle is easy to control.
Notice, here are pictures from the cleaning session (was having so much fun even though it was raining that we didnt get the camera out at the range), maybe next time.
The bolt face after a few hundred rounds fired.
Chamber and upper receiver after firing.
Next difference in bolt carriers, AR-15 bolt carrier, and gas piston rifle carrier.
Notice, the gas piston carrier is basically an M-16 carrier but more metal yet (its heavy), and the embossment for the operating rod to push against is a solid part of the carrier.
The front sight is lined up with the reticle, convenient.
Of course after cleaning, which was very easy compred to a DI rifle.

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June 11, 2009, 01:44 AM
thats one sexy gun, bro.

June 11, 2009, 01:56 AM
That's worth more than my car, I think.

June 11, 2009, 03:53 AM
Actually the upper half was the only expensive part of it. The forward grip came from my heavy barrelled AR (which was only $539), the scope was $160, and the flashlight was a great deal at $36 (when the XRE CREE LED was unheard of yet, they are so bright, and inexpensive). I have a flashlight that I got sent from the distributer in Hong Kong, its 900 lumens, the brightest flashlight Ive ever seen, its as bright as my 1,000,000 candle power spotlight, only it is a small light. That light is too useful, I just use it for everyday things, not for a weapon light.

Bartholomew Roberts
June 11, 2009, 10:26 AM
Actually, there is another easy way to tell the gas piston bolt carrier group from the DI bolt carrier group, just look for the extra wear on the bottom rear of the bolt carrier (and the matching wear on the inside bottom of the buffer tube near the buffer pin retaining pin). That is called carrier tilt.

Looking at what I see on the carrier right now, I'd be interested in seeing what those two areas look like in another 1,000 rounds.

June 11, 2009, 10:55 AM
I have the same scope... I love it! kinda heavy tho...

June 11, 2009, 01:16 PM
I did some research into the "carrier tilt issue", so far there have been 3 examples that are thought by the owners to be carrier tilt in all gas piston ARs, these 3 were gas piston retrofit kits that make use of the original AR-15 bolt carrier and did not have the barrel clamp to hold the piston assembly in place. A quote concerning "carrier tilt" and the manufacturers who make these systems.
"they don't have people actually calling and returning rifles for this problem. This is achieving urban myth status quick."
Also what you are seeing is visible on both bolt carriers, it is light reflecting from the oil, this picture was taken right afterwards from a different angle.

Bartholomew Roberts
June 11, 2009, 01:59 PM
Trust me, that is carrier tilt. Now whether it affects function in a significant manner or not is another question entirely, which is why I would be interested in seeing the pictures several thousand rounds down the road.

Carrier tilt is pretty much inevitable when you grab the carrier by the very tippy-top and push it backwards with a small rod. The AR15 doesn't have any rails so the carrier is naturally going to react this way.

June 11, 2009, 02:14 PM
What brand/model is this gun?

I recently shot a POF USA .223 piston gun back to back with a conventional DI AR. While POF makes a nice product and it certainly stays clean, I though that felt recoil was higher and I was distracted by the moving rod (attached to the piston) when compared to the DI AR. Odd that the moving parts don't distract me as much in AK's or M1A - no explanation.

June 12, 2009, 01:18 AM
Actually there is more wear on the smaller AR-15 bolt carrier (DI) than the gas piston carrier. Over 200 rounds today, no wear more than there was when it showed up. So now Im at over 400 rds, plus.

June 12, 2009, 01:56 AM
Here's a shot of what carrier tilt does to the buffer tube extension after 4-500rnds. If you have carrier tilt it'd be easier to see inside the buffer extension and buffer hold pin.

Posted on sure of the drop-in kit he used but that sure sucks to see. But I think with your one piece bolt carrier (which doesn't have a bolt-on key) will hold up much better than one that doesn't.

And did I miss it or did you not say what "kit" this is? I didn't see any specs on the setup (upper, lower, piston kit) or I'm just blind.

And what's with that un-shrouded firing pin on the old bolt carrier? Bleh!

June 13, 2009, 12:40 AM
Mine is a Bushmaster gas piston rifle upper half(a POF M-4 with a Bushmaster barrel), not a conversion kit.
The photo you showed is one of 3 I found, that was an early gas piston conversion kit without the barrel clamp to hold the system level to the barrel (to keep it straight), and a standard AR-15 bolt carrier, this is why the kits were changed quickly, and some companies added the bigger heavier bolt carriers with solid operating rod embossments.
This is also why I got a gas piston upper half, and not a conversion kit (they look cheap to me). The piston rifle uppers (complete systems built to the rifle upper half) are much bigger stronger systems (POF, Bushmaster, LMT, LWRC).
The only wear showing in my extension tube is what was there from the direct inpingement system.
400 plus rounds with the gas piston upper and counting.
This is a DPMS lower that has had well over 1000 rds put through it by me (DI) and 400 plus with the gas piston upper, and no clue how many by its original owner.

June 13, 2009, 12:46 AM
That's worth more than my car, I think.

I'm curious to know what your driving.

June 13, 2009, 01:53 AM
but the noise is directed a bit differently and its louder than a DI rifle. That's because the "noise" (and all the crap it carries with it) isn't being filtered through the bolt carrier group.

June 13, 2009, 03:12 AM
Its a big difference actually in noise level, the sonic 2 earplugs I normally use were not enough, had to switch to something that blocks more than twice the decibels. My ears were ringing the first time I shot this thing. Yes the crap is sprayed out the front of the gas plug as the piston cycles, the noise is right in front of you.
Aside from the noise, its fun to shoot, a different feel than DI. Not sure my wife will like shooting this one as much as I do, but we will find out soon. She may shock me and really like the difference. A good friend of mine fired it the other day, he looked at me and said "wow, its a brute, theres no mistaking it", but hes used to his 20 inch Colt Hbar.

Bartholomew Roberts
June 13, 2009, 09:08 AM
side from the noise, its fun to shoot, a different feel than DI.

Probably has the different feel because in a DI rifle the "push" from the bolt being unlocked and the bolt carrier being sent backwards comes from inside the bolt carrier.

In the gas piston rifle, it comes from the top of the bolt carrier, so having the push that tiny bit higher above the bore axis may account for the different feel and the reports of slightly higher recoil. I imagine it could also contribute to a little muzzle flip; but the extra weight of the piston system forward probably negates what little contribution there is.

Can we see some pictures of the piston where it comes through the upper receiver? That is one area where purpose-designed pistons have a big advantage over conversion kits. Trying to get a gas piston rod the size of a SIG-556 or even an AR180 into an AR15 upper is no easy chore. Typically the rods are pretty small in comparison to other gas piston rifles.

June 13, 2009, 11:04 AM
This goes to support my theory that GP rifles have the main advantage of being easier to clean. ;) :D

Glad to hear you like it and it turned out good!

June 13, 2009, 11:49 AM
The gas piston rides in the assembly above the barrel and travels in that tube (under the front sight).
The piston pushes the op rod which is in the space that a DI model has a gas tube (only there is a big bushing in that hole as a bearing surface in the reciever).
The delta ring, snap ring, and spring all have a space/ or hole left in them to allow the push rod to enter the reciever unobstructed (alot like a DI model for the gas tube).

June 13, 2009, 01:48 PM
How much weight does this add vs. a comparable AR with a DI system?

June 13, 2009, 02:14 PM
So with the piston, is this similar to an AK action? I know almost nothing about ARs.

June 13, 2009, 02:31 PM
I like that last set of photos, looks just like the system on my FN49. The end plug is almost identical. Definately very cool, and a great improvement. Thanks for sharing.

June 13, 2009, 02:38 PM
An AK piston is long stroke while ar15 pistons are short stroke. I think that's right..

June 13, 2009, 02:41 PM
So with the piston, is this similar to an AK action? I know almost nothing about ARs. No, this is more like an SKS or FAL (you can see the similarities in the pictures).

June 13, 2009, 05:51 PM

June 13, 2009, 11:39 PM
I dont feel any difference that I can notice, I think its very light and balanced. According to Bushmaster the gas piston rifle is 6.5 lbs, the M-4 is 6.22 lbs, so they say barely over a quarter of a pound difference. The assembly is very light.

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