AR-15 ejection.

[LumberZach]

I built an all new AR over the past year and finally took it out shooting last week. It ran great! But I did notice some weak ejection with federal brown box ammo, as in the brass fell in a neat little pile under the rifle on the bench. I looked closer and it almost appeared that there were some marks on the case around the rim (assuming that the extractor is being a little rough with the cases). I tried 3 different types of brass ammo and the rest made me search for the brass, but I am wondering if this is an issue or what you guys think. Bolt carrier is an AIM surplus nitride bolt carrier with the o-ring around the extractor spring. What do you guys think?


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[Hmac]

I'd be suspicous of an overly tight chamber. Who made the barrel? Some of the consumer-level brands are notorious for this.

[LumberZach]

It is an ar-stoner from midway. Do I need go, no go gauges for this, or is there an easier way to check?


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[Hmac]

It is an ar-stoner from midway. Do I need go, no go gauges for this, or is there an easier way to check?

Go/no-go would be more appropriate for headspacing. I'd take it to a gunsmith that could mic the chamber and/or hit it with a reamer or finish reamer if necessary.

[UnaStamus]

Is your barrel marked as .223Rem or 5.56NATO (or 5.56x45)?

[LumberZach]

5.56 for sure.


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[UnaStamus]

+1 on getting the chamber checked. Make sure it's actually 5.56. There are a number of companies producing barrels that are marked as 5.56 that are acually .223. A certain local "angry feline" company is known for this problem. Start there.

[LumberZach]

Ok, good to know. I will definitely check that. Thanks guys!

[JFettig]

Odds that its the chamber are incredibly slim unless you bought a crap barrel and bolt.

Odds are that the gas block isn't straight over the gas port partially blocking it, or gas rings on the bolt are missing, or something along those lines.

[Hmac]

Odds that its the chamber are incredibly slim unless you bought a crap barrel and bolt.

Odds are that the gas block isn't straight over the gas port partially blocking it, or gas rings on the bolt are missing, or something along those lines.

Easy enough to check with a simple glance. Also, make sure the gas key is on tight.

[LumberZach]

I do notice the gas block is slightly off center, but I want to point out that the other 2 types of ammo were shooting well so I am less inclined to believe it is the gas system. How do you guys position gas blocks? I put a level on the receiver and made sure it was straight, then put the level on the gas block.

[Hmac]

I do notice the gas block is slightly off center, but I want to point out that the other 2 types of ammo were shooting well so I am less inclined to believe it is the gas system. How do you guys position gas blocks? I put a level on the receiver and made sure it was straight, then put the level on the gas block.

Slightly off-center isn't a problem. The hole in the gas block is quite a bit larger than the gas port in the barrel.

Most quality barrels come dimpled from the mfgr. Slide the gas block on, tighten the set screws, then drill and pin. Otherwise, a jig is helpful in the installation.

[LumberZach]

I do notice the gas block is slightly off center, but I want to point out that the other 2 types of ammo were shooting well so I am less inclined to believe it is the gas system. How do you guys position gas blocks? I put a level on the receiver and made sure it was straight, then put the level on the gas block.

Slightly off-center isn't a problem. The hole in the gas block is quite a bit larger than the gas port in the barrel.

Most quality barrels come dimpled from the mfgr. Slide the gas block on, tighten the set screws, then drill and pin. Otherwise, a jig is helpful in the installation.

That's what I had heard, so I am not too concerned. I don't believe my barrel is dimpled, but I am surprised/ashamed that I have not heard of pinning the gas block as much.

[Hmac]

That's what I had heard, so I am not too concerned. I don't believe my barrel is dimpled, but I am surprised/ashamed that I have not heard of pinning the gas block as much.

If the gas block loosens while in use, the rifle becomes a single shot at best, and completely jammed up/unusable at worst. Just securing the gas block with the set screws or using a clamp-on gas block is probably "good enough", unless you're one of those sticklers that want's his firearms to be as functional and reliable as they can be. Military rifles require that the front sight/gas block (FSB) be secured with two taper pins. Pinning a low profile gas block follows the same concept for optimal reliability.

[UnaStamus]

Has the Federal ammunition been .223 American Eagle, or the XM193 5.56?
What was the other ammunition? (caliber and brand/model)

It's possible that you got a bad bit of Federal ammo that is underpowered, though it's unlikely. Federal is notorious for having higher than normal pressures, and XM855 and XM193 ammo both tend to be above established pressure limits. It's a rarity, but not impossible.

The possibility of a bad chamber is more likely than people realize. It's worth investigating.
Having said that, eliminate the ammunition first.