AR Preferences- Gas Systems

I installed a piston system on a NFA registered M16 and it runs much cleaner and seems to be a bit more reliable but the down side is that it seems to have a bit higher barrel climb during automatic fire. The interesting part is that the bolt and carrier that came with the piston kit was M16 configured so there was no grinding to be done on the bolt or carrier to engage the auto-sear.

 

To me it really is the Ford/Chevy debate. With quality components either is fine IMHO. I have heard the same thing regarding the muzzle climb from one of the local range masters here that have a couple on their rental rack, but no 1st hand experience. Bought my 1st SP1 back in the late 70's and have several AR's in different configurations as the platform has evolved. All of them are stock, and have had no issues. Another thing to ponder: Are the "stock" parts going to be more plentiful at gun shows/shops as more folks change over? JMT's

Speaking of twists Anyone have a 1 in 14 twist? I have a CAR with the 1 in 14. As I understand it, Stoner originally used that twist with the 55 gr. It definitely has a shorter range, but a very interesting wound channel..

 

Indeed it does. Near as I can tell, it wobbles a bit. Not sure of the proper terminology, but the rear of the bullet appears to be spinning in a slightly larger radius than the tip. As a result, when it hits it becomes unstable and breaks up. I have looked at targets where the bullet has gone completely sideways. A perfect outline of the the 55 grain FMJ. As if I had laid the bullet on the target and took an exacto knife and cut around it. Funny thing is they are never fliers. They are always with in the shot group. All I can say is it works well out to 150 yrds and creates a MUCH larger wound on furry things than the same load out of a different twist.

 

Pretty much have years back. I still have the complete upper, and I do take it out once in a while. I'm an unrepentant AR whore so I doubt if I'll ever part with it. I've come close to rebarreling that upper, but always just end up building another complete upper.

 

I finally went with a piston set up, though only because the price difference between the Adams kit through Bud's was almost the same price as the fancy BCG and gas block I had selected for DI. The kit was easy to install and didn't require any special tools. Both rifles run like tops.

On the issue of heat, a piston does not run cooler in total. The piston does keep the majority of heat and fouling out of the BCG and also no blowback out of the upper. The heat and crud that would otherwise go there instead goes to the gas block and piston. The disadvantage is that depending on how close the gas block of to your hand position and what kind of forestock you are using you might need gloves for heavy fire. It can also make a flip up front sight to hot to handle.

A real advantage to most piston systems is that there is some adjustment built in and you can even shut some off (like the Adams) effectively turning it into a bolt action for precision shooting.

 

Those have a good reputation, but for stretching the dollar, Bud's had Adams factory blems (99% were undetectable) in the $700 dollar range most of the summer.

Wow! Here are a couple with free floated rails for $780 including shippling to your FFL
Adams Arms Piston Mid Length w/ Samson TE Rail Fixed Sights ERGO Grip 556NATO 16" Blem $779.00 SHIPS FREE

Adams Arms Piston Carbine w/ Samson TE Rail Fixed Sights ERGO Grip 556NATO 16" Blem $779.00 SHIPS FREE

The Voodoo barrels used by adams are very good, though not chrome lined. They are nitrided, though, which I prefer because it's a treatment as opposed to a lining that can wear down, It also does not change dimensions, so the bore will not vary as it can with chrome lining. Twist is 1 in 7 on these.

Lots of posts on the Adams blems on AR15.com, very few have had issues and Adams will make it right.

 

If I was starting from scratch then I would try a piston gun.

As it is I would need to add spare parts for a piston gun.

 

My own thoughts- I've been shooting the AR platform since the mid 80's, and it has almost totally been a DI gas system. I don't live in the talcum powder desert, so a piston isn't necessary for me.

Any extra gas tube, pin, carrier key, and a set of rings is all I potentially need to keep a DI rifle's operating system up and running. It isn't hard to clean the bolt carrier assembly, and I have NEVER cleaned a gas tube yet. Never had one clog up at 60,000 cup, it just isn't going to happen. I've had them glow orange, oh my yes.

If a piston rifle has a problem, you will need the specific parts from the company that made the piston. There is no standard in the design and the parts don't interchange between the different companies. If you don't mind this, it's not a big problem then.

E. Stoner made a piston driven AR, it was called the AR-18. For some reason it never caught on. If he could only see what was going on now!

 

All good points, Miss bunny. When I built my pair I bought a spare kit from Adams. I would have spent nearly the same for spare DI parts (the price difference for me I think was $55 between piston or DI), and my purpose for these rifles is WROL where you likely wouldn't be able to go down to your local gunshop and get a new BCG. I can also easily convert them to DI if needed. I really only expect to replace the normal stuff that wears out in any AR platform, though.

 

That's MR. Bunny

The name came from my friends calling my first Jeep (1947 CJ3A) driving around in the fields shooting at rabbits. It didn't help that it had the Buick oddfire six cylinder under the hood and a posi locker in the rear; it would jump and break loose at the same time, and land sideways, leaving two ruts as I kicked up dirt with all four tires. I never had anything like the ole gunbunny ever since.


Here's a picture of the jeep known as the gunbunny. Modeling it is Mrs. Gunbunny. Sorry for the thread hijack, I just wanted to clear some stuff up.

Back to the action!

 

LOL - I stand correcter, sir!

 

IMHO a piston adds needless weight and complexity., and well as increased reciprocating mass, negating some of the advantages of the platform decreasing accuracy, reliability and rate of fire. But some folks think it is better and willing to spend the money for it. For normal use I don't think it makes much difference. I have used AR's in combat and would not touch a piston AR myself. But like I said you spend your money and take your chances.

 

Actually, the 55 grain does perfectly fine through the 1:7 twist.

20" Barrel 1-7 Twist - Dissadvantages??? - AR15.Com Archive

Check the post by Molon down the page. He's collected a lot of data about twist rates into one post.