Gunsmithing AR cycling problems with piston kit

[prplhaz72]

So for a while I have been wanting to try a Adams arms piston kit for an AR. So I finally bought one to try out.

I installed it per the instructions and am pretty certain that is done correctly. I have fired 120 rounds out of it and only had 9 or 10 rounds that have cycled properly. All the others seemed to be short stroked. Many times it did not even open far enough to eject the spent case, other times it ejected but did not catch a new round to put in the chamber, or the action got stuck open because it did not quite go far enough to eject the spent round and it got stuck.

It is a mid length upper, and I am using a A2 length stock with a rifle spring and buffer in it. I am wondering if I have to much weight in the buffer spring combo.

I know there are weights inside the buffer. Can I take one of more of these weights out? Or will that mess up the dynamics of the buffer? Should I switch over to a carbine length system so I can get different weight buffers? I would like to stay with the stock I have, but am open to other options to get this working.

 

[2156SMK]

Re: AR cycling problems with piston kit

Did the gun function good with a regular gas tube before you put the piston system on the upper?

 

[Redcreek1]

Re: AR cycling problems with piston kit

Wolf makes a reduced power AR-Rifle (also M4) spring.

They are only $14.95 and are high quality.


http://www.gunsprings.com/index.cfm?page=items&cID=2&mID=1&dID=79

That should fix your problem.

 

[prplhaz72]

Re: AR cycling problems with piston kit

It functioned perfectly with the DI system.

I tried a Car stock this morning, I had been using a rifle stock. Car stock gave the same problem. I am now wondering if my barrel nut is to thick and it not allowing the piston to move enough. I have a free float on it and it is quite a bit thicker than a Delta ring assembly style handguard/barrel nut. Guess I will put one of those on and give it a try.

 

[monteboy84]

Re: AR cycling problems with piston kit

Not to be a jerk, but I'd sell the piston kit and stick with DI, your gun will thank you by functioning flawlessly. Piston conversion kits are a half-assed fix to a problem that's more imagination and hype than anything legitimate. Even if you get it to cycle reliably, you'll still have problems caused by carrier tilt that won't show on your radar for quite a few rounds. The DI gas system of the AR works great and is extremely low-maintenance if you run it wet with good oil, it's just been talked down by those who cling to the "Craps where it eats" mantra.

Just my $.02

-matt

 

[prplhaz72]

Re: AR cycling problems with piston kit

This kit is just for fun. I love building and tinkering with ARs, so I bought one to play with. If it works, great. If not, no big deal. I will learn a ton in the process and have another AR to play with. It won't replace my DI ARs, just another addition.

 

[Kingsarsenal]

Re: AR cycling problems with piston kit

Hi I'm new here but think iminght be able to help. I've built a lot of ar's some piston. I've found piston is not the way to go. What length is your barrel? I ask because I had a problem short stoking whith a 20" rifle piston from Adams arms. Have had no prob with carbines. Went thru Hel and back trying to get the gap just perfect in between the rod and gas block, and changing springs and stocks. All direction I got from Jim at Adams arms was reduce resistance or increase pressure. He said cut coil at a time of buffer spring; or if that still doesn't work mill gas port hole size bigger at a time. He also told me that's why they don't offer 20" uppers. I ended up cutting 4 coils off spring AND drilling hole in barrel bigger( keep in mind rifle length gas ports are big already)! So after all the bs it worked good but I'll never do it again!

 

[culdee]

Re: AR cycling problems with piston kit

I don't see the advantage to a piston system since so many of them have cycling issues and are ammo sensitive.

 

[Texar2]

Re: AR cycling problems with piston kit

The action of a piston pushing on the bolt carrier goes against the very design of the AR. A piston induces force the AR was not designed to deal with. My AR's are quality rifles and they run great with no problems. Run em wet and feed em good mags.

 

[prplhaz72]

Re: AR cycling problems with piston kit

Well I got this working now. It turns out the FF handguard I had was not approved for it. I thought I read that it was, but I was mistaken. So because of that the barrel nut was way to thick and it was compressing the spring on the piston so much that the piston was not able to travel backwards enough to run the carrier.

I just put a regular old barrel nut on it with the plastic handguards. It runs very good now. I ran through 2 mags fairly quick and then took the carrier out and it was cool to the touch.