The way of the Gas piston

C

copeland

CGN Ultra frequent flyer
Rating - 100%
107   0   1
So it seems alot of manufacturers are going to a gas piston design...

Is this the new direction from the industry? Is it safe to say alot of the aftermarket add on piston kits aren't very reliable?

Just wondering what the consensus is now that DI seems to be going to the wayward...
 
The way I see it - everyone and his dog makes a piston. sys A lot of these piston systems are made by rather small outfits.

It really means that they probably are not tested extensively and the consumers beta the system as it goes.

If you want a piston system for whatever reason, I would probalby stick with those that have been around for awhile (or made by a big company) like HK MR223, LWRCI or maybe the Ruger.

Personally, I will never ever use drop-in kit. Piston is not equal to "better" automatically.

Otherwise, SA80A1 would be the best thing since sliced bread by default....
 
Part of me wonders if there is any large gain to be had over the DI system, but another part thinks its pretty cool to see a 40 year mainstay of the military to be evolving and still getting better.

If i were purchasing one I would get a purpose built one like the Ruger, HK, or that new CMMG that questar has. I wouldn't be dropping in a completely new operating system into a firearm that is designed to work a certain way. I've heard of some problems with the drop in kits, something about bolt tilt or impingement or something like that.

Just finished last months guns and ammo where the looked at a ton of different ar rifles, all the piston guns got good reviews. The writers seemed to feel that accuracy and reliability differences were negligible, but the piston designs were easier to clean and easier on the BCG due to lack of heat on those parts. They did say that the recoil of the rifles felt different, and that they were somewhat more complicated to completely dissasemble.

So take it for what it is. Both are good, but I don't see DI rifles dissapearing anytime soon.
 
I remember someone mentioning that the DI system was patented by colt so it couldn't be used by anyone else...

Course, it's 100% reliable information straight from the internet! [sarcasm]
 
Sorry to ask, I just can't figure out what DI stands for? And do these new piston designs differ from the older (M1 Garand, M14) designs?
 
remington700 said:
Just finished last months guns and ammo where the looked at a ton of different ar rifles, all the piston guns got good reviews. The writers seemed to feel that accuracy and reliability differences were negligible, but the piston designs were easier to clean and easier on the BCG due to lack of heat on those parts. They did say that the recoil of the rifles felt different, and that they were somewhat more complicated to completely dissasemble.

So take it for what it is. Both are good, but I don't see DI rifles dissapearing anytime soon.
Click to expand...

Be wary of reviews done in magazines. Have you noticed that you never see any negative reviews? Either all guns are perfect, or G&A (and the other mags) don't want to ruin the nice relationship they have with manufacturers. I'd rather trust first hand experience here than in a mag.
 
DI? Direct Impingement?
The AG42B, French MAS rifles use direct gas impingement. Gas is ducted back, blows the bolt carrier open.
AR system ducts gas back into an expansion chamber inside the bolt carrier, where the expanding gas forces the carrier to start moving rearward. That's why there are piston rings on the bolt. This unlocks the bolt, and the bolt and carrier are driven open. There is a criticism that fouling in the expansion chamber can contribute to malfunctions. This was certainly a problem over 40 odd years ago in Vietnam.
It has been suggested that the ducted gas AR system contributes to accuracy, because there is less hardware hung on the barrel. Is there any demonstrable difference?
AG42B and MAS are true DI, ARs aren't.
Piston systems may offer some advantages, if well done. Some manufacturers are taking advantage of the "flavour of the month" syndrome to move product. I agree with GT - if you want a piston gun, get one designed and made that way by an established manufacturer.
As far as piston systems go, there are long stroke (M-1, AK), short stroke (SKS, FN-FAL) and tappet (M-1 carbine). The M-14 uses a cutoff and expansion short stroke system. Lots of permutations and combinations on the theme. Many years ago I remember a question being asked about where the gas tank was on a Bren.
Reviews in magazines? How many rifles? How many rounds? In is very hard to reach meaningful conclusions based on limited samples.
 
remington700 said:
something about bolt tilt or impingement or something like that.
[...]
all the piston guns got good reviews.
Click to expand...
Google "carrier tilt". AFAIK, every AR conversion has this issue.
carrier_tilt_040109.jpg
 
It is interesting to note all the discussion on Gas Piston Rifles . I was at the Barrie Gun Club when Questar came out with their 11.5" Gas Piston for testing. Mark was quite generous in allowing various people to fire this model supplying ammunition in various weights ranging from 55 grain, 62 to 75 grain wolf, Privi and just some plain crap guys had in their bags.
This was my first experience with a CMMG gas piston based rifle this short, bottom line it fed fired extracted and ejected everything thrown at it. The accuracy was on par with a standard DI rifle, they must of fired 500rds in a short period.
The great thing was Mark went over right after firing and placed his hand on the Bolt Carrier Group and it was cool, stripped it down and checked it over for carrier tilt and wear issues in front of everyone no problems there.
Overall my first impression after firing this gas piston was very positive, just need to scrape money together for an 11.5" with a quad rail.
 
ops_3329 said:
It is interesting to note all the discussion on Gas Piston Rifles . I was at the Barrie Gun Club when Questar came out with their 11.5" Gas Piston for testing. Mark was quite generous in allowing various people to fire this model supplying ammunition in various weights ranging from 55 grain, 62 to 75 grain wolf, Privi and just some plain crap guys had in their bags.
This was my first experience with a CMMG gas piston based rifle this short, bottom line it fed fired extracted and ejected everything thrown at it. The accuracy was on par with a standard DI rifle, they must of fired 500rds in a short period.
The great thing was Mark went over right after firing and placed his hand on the Bolt Carrier Group and it was cool, stripped it down and checked it over for carrier tilt and wear issues in front of everyone no problems there.
Overall my first impression after firing this gas piston was very positive, just need to scrape money together for an 11.5" with a quad rail.
Click to expand...

Are there any rails that will fit the CMMG piston?
 
In the original AR design, the gas returned into the bolt generates two very distincts effects. Most obvious to all is to apply force rearwards on the bolt carrier to unlock the bold and cycle the action. But it also applies a forward force on the bolt itself, compensating for the pressure inside the barrel and allowing the bolt to rotate freely while it unlocks.

AR piston adaptations do not, to my knowledge, cater for this. They rely on brute force to rotate the bolt and unlock the breach while the locking lugs of the bolt and of the barrel are forced against each other by the inside pressure in the barrel. Because of the added stress on the lugs, it leads to premature fatigue. The original Stoner AR DI gun was simply not designed to work this way.

(This is kind of like trying to unlock a door when the bolt is off center from the hole in the frame and rubs against the little metal thing.)

Guns designed as piston guns from the get-go include engineering solutions such as a longer dwell time, or more generous dimensions on the locking lugs. But these are beyond the scope of all of the drop-in designs that I know.
 
I like how the firearms industry has come full circle. We're right back to 1942. How long has it taken to get the charging handle back to the left side? Now we're back to a piston design. Seems we may as well just reproduce the Stg44 and call it a day.
 
Going to gas piston design? It's more of a throw back than anything else. Most semi's used to be all gas piston before the AR-15/M-16 came out and they wanted something cheaper to manufacture.

even than I can't think of too many semi's besides the AR series that are DI.
 
ops_3329 said:
It is interesting to note all the discussion on Gas Piston Rifles . I was at the Barrie Gun Club when Questar came out with their 11.5" Gas Piston for testing. Mark was quite generous in allowing various people to fire this model supplying ammunition in various weights ranging from 55 grain, 62 to 75 grain wolf, Privi and just some plain crap guys had in their bags.
This was my first experience with a CMMG gas piston based rifle this short, bottom line it fed fired extracted and ejected everything thrown at it. The accuracy was on par with a standard DI rifle, they must of fired 500rds in a short period.
The great thing was Mark went over right after firing and placed his hand on the Bolt Carrier Group and it was cool, stripped it down and checked it over for carrier tilt and wear issues in front of everyone no problems there.
Overall my first impression after firing this gas piston was very positive, just need to scrape money together for an 11.5" with a quad rail.
Click to expand...


I dont think it was a CMMG conversion, I think they are made by PWS.
 
tiriaq said:
DI? Direct Impingement?
The AG42B, French MAS rifles use direct gas impingement. Gas is ducted back, blows the bolt carrier open.
AR system ducts gas back into an expansion chamber inside the bolt carrier, where the expanding gas forces the carrier to start moving rearward. That's why there are piston rings on the bolt. This unlocks the bolt, and the bolt and carrier are driven open. There is a criticism that fouling in the expansion chamber can contribute to malfunctions. This was certainly a problem over 40 odd years ago in Vietnam.
It has been suggested that the ducted gas AR system contributes to accuracy, because there is less hardware hung on the barrel. Is there any demonstrable difference?
AG42B and MAS are true DI, ARs aren't.
Piston systems may offer some advantages, if well done. Some manufacturers are taking advantage of the "flavour of the month" syndrome to move product. I agree with GT - if you want a piston gun, get one designed and made that way by an established manufacturer.
As far as piston systems go, there are long stroke (M-1, AK), short stroke (SKS, FN-FAL) and tappet (M-1 carbine). The M-14 uses a cutoff and expansion short stroke system. Lots of permutations and combinations on the theme. Many years ago I remember a question being asked about where the gas tank was on a Bren.
Reviews in magazines? How many rifles? How many rounds? In is very hard to reach meaningful conclusions based on limited samples.
Click to expand...


Great post, and the bolded part is brilliant!:)
 
OZZ said:
I dont think it was a CMMG conversion, I think they are made by PWS.
Click to expand...

As we clearly indicated on the website (including pictures of the piston system components), this upper utilizes CMMG's newest piston system. These are not DI uppers that have been converted to Gas Piston... these are purpose built uppers that were built from the ground up as Gas Piston units.

The new version of the CMMG gas piston rifles use a 1 piece gas block housing and it is secured to the barrel using BOTH pins and set screws.

The PWS piston system is different. Different design and different components.

Mark
 
Mark, is the CMMG system similar to the LMT system??

The piston looks similar and the BCG has 'skids' on it similar to the one on my LMT BCG...I read it helps against 'tilting'
 
You must log in or register to reply here.
Back
Top Bottom