AR15/M16 Gas Piston Conversion Kit

EddieCoyle said:
The Tommy gun is a blowback design, and it weighs half a ton and takes two men and a boy to operate the charging handle.
Click to expand...

The early Thompsons used some sort of a locking system called a Blish Lock. When the military adopted them the guns were redesigned for a more simpler blow back system.

The Thompson's weight is in the heavy machined receiver, not just the bolt. This gun was WAY over engineered. The grease gun used the blow back system, but weighed much less because it was made of sheet metal stampings.

I think the gas piston system is superior to direct gas impingement. I was never a fan of dumping muzzle gas into the receiver. Piston systems are reliable; witnessed by the success of the M1 and M14. I wouldn't bother to install this system on one of my ARs because the original AR design is more than adequate for the shooting I do. The piston design, however, may find a home in our military rifles.
 
Monadnock said:
latest example:AR-15/M16 GAS PISTON CONVERSION KIT

So ...a lot of useful opining. Does anybody own such a system? And if so, what do you think of it?
Click to expand...

I was going to get the CMMG kit, but you're really limited with the forearms you can use.

Then the Adam Arms kit became available for $299 with the carrier plus it's adjustable, so I picked one up a couple weeks ago. Install was pretty simple since I was building a new 20" upper.

The first time I brought it to the range it wouldn't chamber the next round. I was shooting reloads (55gr FMJ w/ 25gr 2230). I took it home and checked everything out but it all seemed OK. Went back to the range today and brought some XM193. It fired flawlessly! 20 rounds of XM193 down the pipe and then I switched to my reloads. No problem with the reloads at all (So you have to break it in with full power stuff). I also tried some Silver Bear and it didn't even extract since it's so underpowered (tried both gas settings).

As far as recoil goes it did seem like there was less recoil, but I'd have to fire one of my DI guns side by side to confirm that.

All in all I like it and will be picking up a carbine kit when I get the $$$.
 
For now I am sort of sitting back waiting to see what system dominates the market. I am sure at some point either one or two will start to come out as favorites and potentially a standardized system will come out of it. For now the DI system works for me. If you are experiencing ID you should watch this informative video.

http://www.youtube.com/watch?v=iixKGd17hYA
 
Supermoto said:
And the bolts on those rifles run on rails, preventing bolt tilt. This is the problem with conversions on the AR. Plus the DI pushes the bolt forward, floating it while it unlocks so you have less wear while unlocking.
Click to expand...
That is why I don't bother with conversions.

There are serious reliability issues if bolt carrier tilt is not adressed and those who fail to understand this will have long term reliability issues.

My rifle (LMT upper/DPMS lower/RRA trigger) has run reliably through classes, matches, and practice. I see no need to screw with non-standard operating systems.
 
Last edited by a moderator:
Jose said:
That is why I don't bother with conversions.

There are serious reliability issues if bolt carrier tilt is not adressed and those who fail to understand this will have long term reliability issues.

My rifle (LMT upper/DPMS lower/RRA trigger) has run reliably through classes, matches, and practice. I see no need to screw with non-standard operating systems.
Click to expand...

That may be the most important reason to avoid a piston conversion; the AR was not designed to work with this system. I still believe that a psiton system is inevitable for the military, but it will be adopted in a new rifle or a completely redesigned AR.
 
The other fun thing about gas piston uppers is they don't address a glaring weak point in terms of the AR's dirt resistance- the clearances between the bolt carrier and the upper it rides in are still just as bad as they are on a DI gas AR. So, if you get enough garbage (eg, coarse sand) wedged in there, it'll get stuck just like a DI gas one would.

-Mike
 
Good point. I wonder why the reciever isn't grooved in this area to give the crud somewhere to go. This idea was used in early gun barrels to deal with the build up of powder residue; the origin of "rifling".
 
I just atteneded a 3 day Colt M4 /M-16 armorers class. I will stick with the direct impingment until the gas piston systems in the AR are perfected. contrary to what people think they are not perfected yet.
 
Exactly. That's why the military is fielding SCARS and the 416's entry appears to be slowing.

Gammon said:
That may be the most important reason to avoid a piston conversion; the AR was not designed to work with this system. I still believe that a psiton system is inevitable for the military, but it will be adopted in a new rifle or a completely redesigned AR.
Click to expand...
 
stinx said:
I just atteneded a 3 day Colt M4 /M-16 armorers class. I will stick with the direct impingment until the gas piston systems in the AR are perfected. contrary to what people think they are not perfected yet.
Click to expand...

What is lacking that makes them "not perfected yet"?

Specifically the Adams Arms Piston system...
 
Hey, even when they're considered to be "perfected" there will always be those who will tell you they ain't. It's one of the many topics of argument that'll never go away. [wink]
 
sf3pox1 said:
What is lacking that makes them "not perfected yet"?

Specifically the Adams Arms Piston system...
Click to expand...

As I understand it (and someone please tell me if I'm wrong), the main problem with AR piston conversions is bolt carrier tilt. That is, since the piston pushes on the top of the bolt via the key, the carrier will want to travel in a downwards arc as it goes backwards and this can lead to jamming. Ideally, the bolt would be redesigned with tracks or some sort of guide to prevent this. Presumably something like the HK416 has a fix for this built in and uses a slightly different upper design.

Personally, I think there's a good reason every other battle rifle uses a piston but I do agree with the lack of standarization being an issue if you want a piston AR.
 
PaulD said:
As I understand it (and someone please tell me if I'm wrong), the main problem with AR piston conversions is bolt carrier tilt. That is, since the piston pushes on the top of the bolt via the key, the carrier will want to travel in a downwards arc as it goes backwards and this can lead to jamming. Ideally, the bolt would be redesigned with tracks or some sort of guide to prevent this. Presumably something like the HK416 has a fix for this built in and uses a slightly different upper design.

Personally, I think there's a good reason every other battle rifle uses a piston but I do agree with the lack of standarization being an issue if you want a piston AR.
Click to expand...

That is the problem with standard carriers and even the lesser quality brand companies' kits. The Adams Arms bolt carrier is said to have fixed that issue due to it's design. It does not have the problem with carrier tilt, which seems to have been proven thus far in some very harsh conditions.
 
Last edited:
PaulD said:
As I understand it (and someone please tell me if I'm wrong), the main problem with AR piston conversions is bolt carrier tilt.
Click to expand...
sf3pox1 said:
The Adams Arms bolt carrier is said to have fixed that issue due to it's design. It does not have the problem with carrier tilt, which seems to have been proven thus far in some very harsh conditions.
Click to expand...
Does the Bushmaster gas piston conversion kit exhibit this "bolt carrier tilt" problem?

CLMN
 
Before I purchased my LWRC piston upper I researched the carrier tilt issue and it was an issue for the first generation of LWRC piston uppers... but since then, LWRC has made changes and carrier tilt is no longer an issue.
 
Okay ...bolt-carrier tilt has been discussed, now what of rifle accuracy?

Does all of that extra hardware effect the behavior of the fired round?

I'm curious about the effect of things like barrel harmonics on rifles where floating the barrels can have such a good result.

Any experience regarding pre-installation (of the gas-piston system) versus post installation on accuracy and repeatability (MOA and such)?.
 
Carrier tilt, and gas issues. There is a reason some of these kits have gas regulators on them. For what its worth We were told Colt has gun ready to go in the event the Military decides to make the move to Gas Pistons. THe HK 416 was mentioned and several Military armores and civilian contractors stated they are not the super weapon evryone thinks they are. YMMV
 

Similar threads

Ar15 new handguard
Replies
2
Views
147
allen-1
allen-1
Gas tube position new PSA .300 Blk upper / Sig lower & BCG
Replies
12
Views
507
pastera
pastera
Glock 22 to 9mm Conversion Barrel and mag question
Replies
12
Views
1K
allen-1
allen-1
Retro/Fixed Carry Handle AR15s Pictures and discussion thread
3 4 5
Replies
121
Views
8K
Marty McFly
Marty McFly
ar15 parts questions
Replies
2
Views
484
paul73
paul73
Back
Top Bottom