AR-308 extraction problem

[n10sivern]

Ok AR gurus, I have a question. It's on a DPMS platform AR308 in 7mm-08. Just rebuilt this rifle using a different receiver set and bolt. It was a side charging before and I didn't like it so I went with a regular receiver set. It has an adjustable gas block and is being run with a suppressor. It is having extraction issues and I think it's the bolt, just wanted to run it by y'all before I started buying new parts. With a mag full it would feed the next round but jam the spent case in with it. I started loading 1 round at a time in the mag. It isn't short stroking as it'll lock back on an empty mag. 20% of the time it'll eject the brass. 40% of the time it will lock back with the spent brass just sitting on top of the mag loose. The other 40% of the time the bolt locks back and the case is still in the bolt kicked out sideways. Any ideas?

[B. Lumpkin]

It sounds like it's extracting the brass fine, but not ejecting. Is that the jist of it?

[n10sivern]

Yes. I should have said ejection and not extraction

[Moleman-]

You list the bolt as having been replaced. If it worked fine with the other bolt can you change it back to the original bolt to see if the issue still persists? Shouldn't be an issue as usually the only difference in the BCG between standard and side charging is in the carrier. If the bolt extractor and ejector check out as fine, I've seen the same thing in carbine length guns that were over gassed. With the can and adjustable gas block that could be something to look at as well. Usually there are some decent ejector and extractor marks on the brass that are similar to what you'd get with too hot of loads, but are caused by the bolt unlocking too early.

[n10sivern]

I can't get the other bolt back as I sold it with the receivers. I know you mentioned carbine length, this rifle is rifle length 24" barrel. I have the adjustable gas block set to where it just locks on empty mag so it shouldn't be over gassed.

[Gar]

My first thought is to check the ejector pin and spring aren't bound up and are moving freely.

[n10sivern]

I actually found another bolt in my parts bin. I'm gonna try that and if it works I'll just o-ring the spring on the other bolt and retry it.

[lefty o]

id open the gas sys up just a little. just because it has enough gas to work the bolt back far enough to lock it back, does not necessarily mean it has enough to properly function.

[Electric88]

I agree with lefty. Open the gas up some more and see if that helps.

[n10sivern]

I tried it with the gas opened up. It almost 100% fed the next round while jamming the spent brass in the ejection port.

[Moleman-]

With a suppressor and an opened up gas port it is easy to over gas them which can mimic under gassing as now they have to deal with much higher extraction forces. If you are shooting the gun the same as how you set the regulator (can on or off) and worked it up from not unlocking, I wouldn't mess with the port diameter if it ran well before the upper swap, especially before checking for misalignment of the gas block. Here's an excellent rundown of what I'm talking about http://www.ar15barrels.com/prod/operation.shtml Let us know how it does with the O-ring around the extractor spring and I'd clean out the ejector hole while I was at it. After your last post that's where I'd concentrate. I've had bad extractors, and springs right out of the box.

[Rick45Colt]

I had a DPMS like yours in 308 and I tried all kinds of things including but not limited to new buffer, buffer spring, etc. According to the guy at my local gun shop DPMS had mixed and matched some AR15 parts instead of the beefier AR10 type parts. Extracting was the exact issue that I been having with that rifle. I will never purchase a DPMS or Bushmaster for that reason!!!!

[Electric88]

I had a DPMS like yours in 308 and I tried all kinds of things including but not limited to new buffer, buffer spring, etc. According to the guy at my local gun shop DPMS had mixed and matched some AR15 parts instead of the beefier AR10 type parts. Extracting was the exact issue that I been having with that rifle. I will never purchase a DPMS or Bushmaster for that reason!!!!

I'm not sure what the guy at your local store was trying to get at. There are certain parts in the AR10/AR308 that can be pulled from AR15s to be used. Among these are trigger group and gas tube. They are literally the same size. Using them interchangeably will not adversely affect the gun in any way. Anything in an AR15 that is undersized with comparison to the AR10/AR308 will not even fit into the gun. No way to mix them up.