AR help

[Oneaudiopro]

I went to the outdoor range in Petaluma today and took my newest aquired toy, a Stag model 1 AR. I racked the 1st round in the chamber, pulled the triger, click..........nothing. I removed the magazine, ejected the live round and started all over again. Thinking it was a bad round, I started again........same thing. There was no indentation on the primer and the bolt wouldn't seat the round all the way into the chamber.
I took the 150rnds I was going to shoot in the AR and proceeded to fire all of them in my Ruger mini-14..................EVERY ONE went bang.
When I got home I looked down the barrel and also into the chamber, all appears ok. I disassembled the AR and dropped a round into the chamber and it won't seat fully. I ran a brush down the bore as well as the chamber..........won't seat a live round.
Any ideas. I've only fired 20rds thu it since I bought it about 6mos ago, no hitches, all 20 fired flawlessly.
Any help or ideas would be greatly appreciately.

[riddler408]

sounds like your head spacing is off

[SactoDoug]

That sounds really weird. What caliber does the barrel have stamped on it?

[NewbieDave]

Are you letting the bolt fly forward or riding the bolt into the chamber?

[Oneaudiopro]

Couldn't be head spacing because the round is about 1/8-1/16 of an inch from seating fully. My first thought was maybe part of the neck sheared off and was stuck in the chamber, but I can't see anything like that although its hard to get a great view into the chamber.

[bajadan]

-Does the BCG fully engage on a empty chamber?

-Definitely sounds like headspace issue. If its a factory rifle they will warranty it. If you have a set of Go-No-Go gauges you can find out real fast what the issue is.

[Oneaudiopro]

Bolt isn't in the rifle, no need, a round wont seat fully when its dropped into the chamber. I have the upper and lower seperated right now.
Its a 5.56 stamp on barrel.

[RobGR]

20 rounds fired flawlessly the first trip, second trip, you had issues. Did you disassemble your bolt after the first trip? If yes, CHECK IT, strip it down and reassemble.

A photo of the chamber might help too.

[Oneaudiopro]

Yes.....BCG seats fully when not loaded with a round in the chamber.

[RobGR]

Hopefully your chamber doesn't look like this guy's chamber.

Photo of the face of your bolt too.

[bargasm]

Easy, Mini 14 > AR 15! Just kidding, sorry I don't have anything real to bring to the table, best of luck

[SactoDoug]

Since you successfully fired it six months ago, it sounds like you have debris in the chamber.

[Munny$hot]

Before you start checking head space lube your bolt and drop some oil into the exhaust ports. Usually a newer or dirty AR will have these problems

[SB1964]

You said the bolt is out of the upper. Is everything out? Remove the handle & BCG. You should be able to use a small light & look into the chamber. You can look through the back of the upper receiver. Something is wrong with the chamber. Its not a cycling issue, don't lube the gas tube, or key. Don't stick a pipe cleaner in there either. Oil will cause more deposits to accumulate inside. Another comment from a non AR owner.

[Heretodaygonetomorrow]

Tell us about the ammo you tried to fire. By any chance are they reloads that have been previously fired in the Mini?

Fired brass expand to the shape of the chamber they are fired in. If you fired the rounds in the Mini (or another gun), and did not resize with small base dies, it's possible that the brass is simply too large to chamber in the AR, whereas the brass will always fit back into the chamber it was last fired in.