I was out shooting yesterday and in the middle of a mag, the bolt locked back half-way through its stroke.  

I immediately tried SPORTS and no matter how hard I pulled on the charging handle I could not get the bolt freed up.  I had to quit for the time being.  

The bolt (carrier) was frozen just behind the ejection port.  I ended up banging the stock on the bed of the pickup and pulling the charging handle back as hard as I could and the bolt let loose.  

I pulled everything apart and there were no signs of anything being broken.  

Also, it was somewhat dirty (about 100 rounds w/o cleaning) but was lubed.  Besides, I've run hundreds of rounds w/o cleaning without ever having a stoppage.  

After the inspection, I put it back together and it ran fine after that for another 2 magazines.  

WTF? over...

My guess is a primer got hungup somewhere.

Were there any scratches on the BC? I wonder if the buffer retaining pin hasn't popped up just a bit too high, enough to catch the BC?

Quoted: Were there any scratches on the BC? I wonder if the buffer retaining pin hasn't popped up just a bit too high, enough to catch the BC?

There would have been considerable damage if that happened.  Adn it would have still been out of place when he opended the gun up.  I owned a lower that had a bad retaning pin.  It damaged the lower when itpopped out.  Previous owner had ignored the problem.

TRG

I'm still baffled.  

Anyone else have this happen to them?  

Yup

Primer popped out and got stuck in the lower b/c.

Dropped the mag, pulled the charging handle while gently smacking the butt stock on the shooting bench and the b/c broke free and the primer popped out the mag well on to the floor. It was wedged shaped.

Quoted: Yup Primer popped out and got stuck in the lower b/c. Dropped the mag, pulled the charging handle while gently smacking the butt stock on the shooting bench and the b/c broke free and the primer popped out the mag well on to the floor. It was wedged shaped.

Thanks dog.  

That must have been it then.  I didn't notice any primer pop out but then again, I just wanted to get my rifle up and running so I could run some more drills so I wasn't paying attention to anything like a primer that might fall out.  

I have no other explanation for this.  

It is troubling however.  The damn bolt was locked up tight.  

I had to really work the thing to get it running.  Hope it never happens when I need it for real.  

Drives home the basics of cover and having a back-up weapon.  

Hell, give me suppresive fire!!!

Quoted: Drives home the basics of cover and having a back-up weapon.

That and using suitable ammo.  

Reloaders hate surplus ammo with the staked primers because it's more work to reload the brass, but it prevents this type of thing from occurring.

Is Q3131A "suitable ammo."  

That's what I was using.

No wolf or reloads in my AR.  

I'm still not convinced the problem was a primer but I haven't heard any better explanation yet.

Thanks.  

Quoted: Is Q3131A "suitable ammo."   That's what I was using.

I've always been told that it was suitable...