I took my son to the range on saturday and brought 2 magazines for him to shoot.

We shot through 1 complete magazine and when I put the second mag in, I pulled the charge handle and let it go, sat down to fire the first round and only had a *click. I looked at the ejection port and the bolt was not seated. It's as if the teeth of the bolt (bear with me, I don't know the exact terms) were resting on top of the chamber teeth, not interlocked as it should be.

I couldn't get it to reseat so we set the rifle aside and shot his .243.

After getting home I had to take the rifle apart since I couldn't get it in place. I tore down the BCG, cleaned & lubed everything and put it back together. It seated for the first couple of pulls but then got stuck again. It almost feels like it's getting stuck in the BCG, it doesn't cleanly/smoothly move within it.

It's a bravo company upper and only has a couple thousand rounds through it.

Any ideas?

I would carefully inspect the lugs and slots of the bolt and the barrel extension for any damage.
As you probably know, the bolt should rotate slightly (and freely) when it’s moved back and forth. Did you check for that?

And then there’s the question of how freely the bolt moves in the carrier. Did you try moving it back and forth by itself without the cam pin? If it seems like the bolt is getting stuck in the carrier, check for carbon buildup or possibly the presence of some bit of debris inside the carrier where the bolt fits.

No expert by any means, but I had to lightly file a new cam pin to make it cycle smoothly. This video may shed some light.

https://www.youtube.com/watch?v=lm5CggERUNo

I'm pretty sure that cam pins are a hardened part. I don't think I would file one.

quote:

Originally posted by sigfreund:
I would carefully inspect the lugs and slots of the bolt and the barrel extension for any damage.
As you probably know, the bolt should rotate slightly (and freely) when it’s moved back and forth. Did you check for that?

And then there’s the question of how freely the bolt moves in the carrier. Did you try moving it back and forth by itself without the cam pin? If it seems like the bolt is getting stuck in the carrier, check for carbon buildup or possibly the presence of some bit of debris inside the carrier where the bolt fits.

I did inspect it, the lugs look fine. No, it no longer moves freely in the carrier.

quote:

Originally posted by Shaql:

I did inspect it, the lugs look fine. No, it no longer moves freely in the carrier.

This suggests a likely problem with the gas rings. Check them and ensure one is not mangled and that the 3 rings do not have the spaces lined up.

The Bolt should move freely in and out within the BCG with a degree of resistance. Testing for the proper amount of resistance can be achieved with extending the bolt then setting it vertical on it's face and see if the bolt collapses.

Hope this helps.

Andrew

quote:

Originally posted by El Cid 92:

quote:

Originally posted by Shaql:

I did inspect it, the lugs look fine. No, it no longer moves freely in the carrier.

This suggests a likely problem with the gas rings. Check them and ensure one is not mangled and that the 3 rings do not have the spaces lined up.

The Bolt should move freely in and out within the BCG with a degree of resistance. Testing for the proper amount of resistance can be achieved with extending the bolt then setting it vertical on it's face and see if the bolt collapses.

Hope this helps.

Andrew

There is a fair amount of "side to side" movement of the rings. But the dont look mangled. The bolt does not move when set on end. It takes a bit of push to get it to move.

I just saw a YouTube video. I guess I'll be trying some new gas rings?

There must be something that’s interfering with the free movement of the bolt in the carrier. However, even if the rings had been damaged (unlikely unless abused), the bolt could not have been inserted into the carrier if they were bad enough to prevent the bolt from moving. It can’t hurt replace them, but I will be surprised if that cures the problem.

I’m still leaning toward the likelihood that there is something like a buildup of carbon, or more likely, that a large chunk of carbon broke free inside the bolt cavity and is blocking the bolt’s rearward movement. Perhaps you’ve already checked and eliminated that possibility, but if not, that’s what I would look at.

The one last thing I can think of is to check to ensure that the ejector spring pin and extractor pin are centered in the bolt and not dragging on the carrier.

quote:

Originally posted by sigfreund:
I would carefully inspect the lugs and slots of the bolt and the barrel extension for any damage.
As you probably know, the bolt should rotate slightly (and freely) when it’s moved back and forth. Did you check for that?

And then there’s the question of how freely the bolt moves in the carrier. Did you try moving it back and forth by itself without the cam pin? If it seems like the bolt is getting stuck in the carrier, check for carbon buildup or possibly the presence of some bit of debris inside the carrier where the bolt fits.

This is what I suspected when I first read about your problem. Take apart the BCG and clean the carbon out where the bolt goes, and the bolt also. The rings can be having a hard time and getting hung up on the carbon.
Good luck.

worn/bad gas rings are the opposite of your problem and seem unlikely. Everything moves way too easy when that happens...
If you put the bolt carrier on a hard surface and manually move the bolt back and forth is it somewhat easy but with some modest resistance?
when you drop the bolt into the upper and then push to close it what happens? does it move and lock up (bolt carrier even with the end of the upper) or something else?

quote:

Originally posted by rtquig:

quote:

Originally posted by sigfreund:
I would carefully inspect the lugs and slots of the bolt and the barrel extension for any damage.
As you probably know, the bolt should rotate slightly (and freely) when it’s moved back and forth. Did you check for that?

And then there’s the question of how freely the bolt moves in the carrier. Did you try moving it back and forth by itself without the cam pin? If it seems like the bolt is getting stuck in the carrier, check for carbon buildup or possibly the presence of some bit of debris inside the carrier where the bolt fits.

This is what I suspected when I first read about your problem. Take apart the BCG and clean the carbon out where the bolt goes, and the bolt also. The rings can be having a hard time and getting hung up on the carbon.
Good luck.

I think that was it! I ran a .270 wire brush through the bolt carrier and it still takes some pressure but not near what it was. The good news is that when using the charging handle, it seats every time.

The bad news is I mangled my detent spring and now I need to go get another.

Thanks so much for the help!

Also sounds like the bolt group could use some lube. The AR system needs lube. A good amount of it.

Pick whatever lube you like. Some use CLP, others use whatever gun oil/lube. Some of use use grease.

Whatever you choose, generously lube that thing so it is nice and slick.