My wife and I went out to shoot the M82A1 the other day.  We brought about 50 rounds of factory CBC M33 660gr ball.  After putting about 30 rounds through it, the next round fired, and chambered another round, but didn't fire.  It was very difficult to pull the bolt back, but I finally got it and the un-fired round ejected (no primer strike).

I let the bolt slam closed on an empty chamber and then tried to open it again.  Again, VERY difficult.  Almost needed to mortar it or tap with a mallet, but finally got it open.  I put a spent case in perpendicular to act as a bolt hold open after inspecting it (all looked fine), and then decided it was time to go.  The barrel seems fine - it moves.  I took the upper and loser apart...  the bolt cycles normally in the lower.  The upper looks fine.  I put them back together and it still had a really hard time cycling the bolt.

Thoughts?

Did this ammo come from SG Ammo?
https://www.ar15.com/forums/Armory/Pierced-primers-on-M107A1-CBC-M33-Ball/3-539176/

I was piercing primers on my 107A1, and then the primers will lock up the firing pin and bolt:

https://youtube.com/shorts/RdDP6np8dk8?feature=share

Interesting - I will have to look at the brass to check.  Your video may help a lot as well.

The CBC ammo I got; pretty sure I've had it for close to 10 years and used it with my M99.  I *think* I got it at AIM Surplus a long time ago...  but dunno - could be from SGAMMO.  I just know I've had it for ~10 years.

@50cal

Should be able to give you some help.

Is there anything stuck where it shouldn't be, small shaving of brass? Anything loose or bent? Enough lube on all the moving parts?

The carrier being hard to open on an empty chamber is very odd. The only time I ever remember seeing that happen was when a piece of brass or primer shaving got into the firing pin channel of the bolt itself and kept the bolt from rotating to come out of battery.

Take the carrier out of the rifle and try to remove the bolt. With a light, look in the firing pin channel from the rear of the bolt. Sometimes something will wedge in their almost like cold welded itself in.
You may need a pick or a punch to reach up in there and get it loose.
Be aware that there is also a small piece of rod welded into the bolt and it only shows when you look into the bolt from the rear. This keeps the rifle from firing unless the bolt is fully rotated. If you look at the firing pin, it has cut outs in it to only allow the firing pin to go fully forward when the bolt is completely in battery.

You guys nailed it!

That was precisely the issue - outlined exactly how to fix in the short video from Buffman_LT1 above.  It's amazing how such a small piece of brass is able to stop such a mighty rifle, dead in its tracks.  

As soon as I pulled the bolt out of the carrier and tapped it, the small primer - now smashed into a 1/3 cylindrical shape - fell out.

Pics of it here , in case anyone is interested.

Thank you!

Damn!

Was it the entire primer? Check your brass and make sure the whole primer came out. That way you don't lose another primer when you reload the brass.

Another couple of ???'s, is this reloaded ammo, remanufactured... if so, was the primer pocket reamed or swaged? Loose pockets or hot load?

Next time you shoot said ammo, keep an eye on the primers after shooting a mag. At least now you know what to do if you have a similar issue.

Factory CBC ammo I bought ~10 years ago or so.  Was sealed in the boxes with the plastic (also sealed) package around it. I've shot a few hundred rounds of it with my M99 and M82A1 and this is the first issue I've had with it.

Glad to hear you got it fixed!

It’s great you got it fixed with minimal effort. It’s amazing some people returned rifles to us over in credibly simple things that would have saved shipping a heavy ass shipping box both ways.

But then, I did get in trouble issuing call tags for return shipping to us a few times.