Another AR problem

[danhr]

So I finished my AR build.... And I have had a few problems..... The latest, I think I might need input from someone with more experience.

Mega upper/lower/barrel 18" barrel mid length gas system
Seekins precision adjustable gas block
JP low mass BCG with enhanced high pressure bolt
JP buffer spring with DPMS buffer. The rest of it really doesn't matter,I don't think.

Anyhoo... Had a few hiccups (magazine catch was not catching) I finally got it running and dialed in the adjustable gas block (open up gas block until bolt locks back and give it an extra 1/2 turn.... Well actually I only did 1/4 turn because it was 30* when I was doing it).

Anyways, I get about a hundred rounds through it, both suppressed and unsuppressed. As I was playing around at 300 yards, getting some dope, it stops ejecting. I don't believe it to be gas related, because the easiest way to boost up gas is to throw the can on. With the can on, same problems.

So after a round is fired, the case is extremely hard to get out of the chamber. Like, in order for me to extract the spent round, I have to put the stock against my chest and pull the charging handle with both hands (I am no meat head, but I'm not a very small man.... I'm 6' 275 lbs) or I have to mortar it out. It will easily hand cycle fresh rounds, like a hot knife through butter.

I thought it was maybe the ammo, so I tried a few different brands and they all have the same problem.

The original ammo was ZQI, and then I used Hornady steel match, and then federal gold medal match.

I want to think the headspace is too loose, but I don't have a go/no go gauge. And it seems pretty hard to believe that the headspacing would change all of a sudden, after 100 rounds.

Any ideas?

[gghbi]

First thing I would do is get a good visual on the chamber to see what it looks like. I wonder if there is an obstruction that is not preventing the cartridge from going in, but keeps it from coming out. You stated you can hand cycle fresh rounds, is that in and out? I would pay particular attention to the throat area. Any marks of distinction on the fired cases?

Let us know how it goes, good luck.

[arjohnson]

Sounds like the chamber is out of spec, to tight. Works for a little then after getting dirty cases get stuck.

Clean the chamber and try again and see if it repeats.

[dkf]

Chuck a .223/5.56 chamber brush up in a drill, put on some solvent and scrub the chamber. Mega usually nitrides their barrel and that process can leave crap behind which can get in the way.

[bogey1]

I didn't know you could headspace a ar15.

[awfroadan]

As others said clean the chamber. Suppressors make a big mess inside an AR chamber area. Are you running your gun wet or more dry? It wouldn't be a bad idea to get gauges to check your head space to rule out that as an issue.

[chp1911]

Chuck a .223/5.56 chamber brush up in a drill, put on some solvent and scrub the chamber. Mega usually nitrides their barrel and that process can leave crap behind which can get in the way.

What exactly gets left behind?

[poconopashooter]

I don't believe anything is left behind. I though Nitriding is a chemical treatment of the metal and it doesn't change the dimensions at all.

[MasonArmsGunsmithing]

A good chamber cleaning is the first thing I would do. Most likely the headspace is not the issue if you didn't have issues right off the bat. That being said it would be a good idea to check it anyway. What does the brass look like? Sometimes if your chamber is rough it will give you extraction problems like this. Anytime you have an extraction issue, the first thing to look at is the brass, it gives you a perfect mirror image of the inside of your chamber.

[danhr]

I didn't know you could headspace a ar15.

The barrel extension gets moved in or out. Typically not a issue with an ar-15, as everything is Mil-spec

However with .308 ARs, pretty much everything has to be checked or adjusted

The rifle was originally lubed with grease... Started having problems, so I hit it with old fashioned CALL, to rule out that problem.

I will try cleaning it, but if the problem is occuring after the carbon build up after 100 rounds, the damn thing is getting sold. That's almost laughable that one can't run more than 5 magazines before it's so dirty it's malfunctioning.

I will try cleaning it anyways and shoot a few rounds this weekend and post pictures of the brass