Cause of a stuck case?

[Tim K]

I was out today with a new rifle. AR, 16" mid length gas, lothar barrel. I ran a few rounds of M855 through it, then some factory 55g. It all functioned fine.

I then loaded a mag with my pet accuracy load, 77 SMK, 24g Varget, and stuck the case on the first round. I didn't have a cleaning rod, so that ended the day. After getting home and poking it out with a rod, it was obvious the rim had been ripped off. It was also obvious the case was stuck pretty tight.

This was my first time with a stuck case. What are the potential causes?

[ray1970]

I don't have any data in front of me and haven't used Varget for my 223 loads in years, but isn't 24 grains a bit much for a 77gr projectile?

[ray1970]

Ok. I checked. That load doesn't seem to be excessive. Did you put a pretty decent crimp on it?

[Tim K]

No crimp. This load has functioned flawlessly in at least 5 other rifles. Those were all 18" with mid length gas. This one was 16" mid length.

[ray1970]

No,crimp? Ok. Here's my theory. Only a theory. Perhaps, as the round is slammed home by the bolt carrier assembly, the bullet is being jarred forward from the inertia as the shoulder slams into the chamber. With the bullet jammed against the lands of the rifling, an over pressure condition is caused when the cartridge is fired causing it to stick in the chamber.

I think we can at least agree that since the other loads seemed to function just fine that the problem just about had to be with that one particular load.

Sorry. That's all I have to offer in the way of advice.

[Tim K]

You may be right, Ray. That load hasn't done that in other rifles, but it might have had a loose neck for some reason.

[ray1970]

Years ago I was trying some loads in an AR for accuracy. I didn't crimp them because I didn't want to distort the bullet any and degrade my accuracy. I had to pause and upload during a string of fire one day and when I pulled the charging handle back to un chamber the round all I got was the case. Powder went everywhere. I actually had to tap the butt of the rifle on the ground to retrieve the projectile. It had a neat little ring of dashes on the ogives where it was stuck on the rifling lands. Ever since then, if I load for a semi-auto rifle I just make sure to crimp.

You could have a totally different problem. I really have no idea.

Best of luck getting it resolved.