Went out to shoot in the new 80% lower a while ago.

Had 2 20 round mags and a 10.

The scope was adjusted but then it started short stroking sometimes.

Did the 1 shot drill and same on locking back the bolt only it got worse.

Pulled the bolt carrier out and removed the bolt.

Problem was the gas rings were toast.

They would not hold the carriers weight,one of the rings was missing about 1/3 and the others were wore bad.

This is a Colt upper that has less than 300 rounds shot thru it.

Now a question go back with the 3 gas rings or try the one piece spiral locks?

MPC marked bolt?

I've never seen the need to change from the original design.

Colt factory bought whole back in the early 80's.

Have 2 and the other has been thru more rounds than this one.

Guess sometime stuff just happens.

Need to gather some other spare parts as well,one never knows.

There's something going on to have lost the rings in less than 300 rounds, doesn't really matter whose rings they are. Colt marked bolts are some of the best out there and I'm wondering if someone swapped your bolt. That's why I asked if it was marked MPC.

I'd be inclined to take a close look at the carrier. Or it might be that the gas rings were cracked during installation.

Was it lubed recently?

Shooting it dry can = early wear out issues.

It was wet,i don't know how it was run before i got the upper.

I don't know what happened to it.

It seems that folks are now trying to hoard gas rings.

I have some coming as well as some of those one piece rings.

Will be something of a test to see how they work.

And just for fun got another complete bolt coming.

You never know.

Check the inside of the carrier, it should be chrome lined and smooth but if it's not chromed, it might have a rough spot in there from the broken ring.

A spare bolt and carrier are good to have.