What are the odds? New Failure I have yet to see.

[Cdub_NW]

So here is a new one for everyone to laugh at (or cry)....

During a range session today, I experienced a failure I had never seen before, heard of, read about, thought could even happen....

During a string of slow aimed fire off a bipod and rear bag the rifle failed to go into battery, I the round in the chamber and attempted to cycle the bolt with no joy. The sound was odd and I felt it was wise to stop and get it back on the bench to diagnose the failure. I was done for the day anyway, glad I stopped and didn't try to force anything.

The Bolt would not seat into battery, I guessed based on where it was making contact that there was either a blown primer or a rock stuck in the BCG where the locking pin goes through the bolt inside the carrier that was stopping the bolt from being able to slip back inside the carrier. This presented a problem where I could not open the upper receiver from the lower as the bolt was back just far enough it would not clear the buffer tube joint of the lower. At this point I needed to get the BCG out somehow (and forgetting that I owned a barrel vise) I did not want to attempt to get the barrel nut off without using an action rod to risk destroying my upper or barrel. Came to the decision to cut the back half of the carrier to get the bolt out. This was a budget BCG anyway so not the end of the world to destroy a $60 item to save the upper.

After getting the BCG cut and removed to my surprise the culprit was a popped primer that had magically gotten stuck inside the gas key.. yes you read that correctly, inside the damn gas key. It is a near perfect fit (I do not recommend testing this yourself as it will take a lot of cursing and some time to clear). The gas tube looks fine, glad I didn't try to hammer the bolt forward or I likely would have destroyed that too. But something for you all to put in the back of your minds as a possible point of failure. but really, what are the damn odds of this one!!!?? Ugh.....

[The Rat]

Wow. Either buy a lottery ticket or stay home the rest of the week so you don't get in a freak car crash!

How did you get it out of there?

[Clusterfrack]

Thanks for the detailed post @Cdub_NW. I moved the thread to our rifle subforum.

I once had the anvil from a blown primer get jammed between the bolt shaft and the carrier. Your malfunction is way worse.

[Cdub_NW]

Wow. Either buy a lottery ticket or stay home the rest of the week so you don't get in a freak car crash!

How did you get it out of there?

First tried compressed air to blow it out.. failed. moved onto a pick and slowly wiggled it up the inner sleeve of the gas key to get the rim above the top lip so I could grab it with some small needle nose plyers. It took about 15 min of slow work to get it out.

[M2CattleCo]

If that’s a BCM barrel it’s probably the barrel. I have had a few of them and they tend to be hard on brass, pop primers, and show pressure signs before a better quality barrel.

[Clusterfrack]

If that’s a BCM barrel it’s probably the barrel. I have had a few of them and they tend to be hard on brass, pop primers, and show pressure signs before a better quality barrel.

That hasn't been my experience with the 4 BCM uppers I've owned. What are your concerns with these? What do you consider higher quality?

[theJanitor]

I had a popped primer get into the BCG via the cam pin orifice. The BCG locked up partially in the RE and it was a major PITA to get the gun freed up

[M2CattleCo]

That hasn't been my experience with the 4 BCM uppers I've owned. What are your concerns with these? What do you consider higher quality?

All the ones I’ve seen were on the tight end of all the chamber and bore dimensions. Makes em prone to pop primers.

[Clusterfrack]

All the ones I’ve seen were on the tight end of all the chamber and bore dimensions. Makes em prone to pop primers.

Mine have had no issues with factory 5.56 ammo, and seem to be more forgiving than more "accuracy" oriented barrels like LaRue, despite having equivalent accuracy. The blown primers have all been my reloads from range pickup brass, so no surprise.

[Wake27]

Mine have had no issues with factory 5.56 ammo, and seem to be more forgiving than more "accuracy" oriented barrels like LaRue, despite having equivalent accuracy. The blown primers have all been my reloads from range pickup brass, so no surprise.

My experience as well though I don't shoot reloads. I've had blown primers with Noveske, Geissele, and a smith built Criterion Core barreled upper and at least the last two were symptoms of a larger problem. I've owned BCMs since 2013ish and after owning at least half a dozen barrels and/or complete uppers, that was never an issue. BCM is actually the king of reliability for me with far more sample sizes and less issues than any other manufacturer. I was big sad when a MK2 upper I got in the last two years had significant issues and needed a trip back to the factory but they did handle it better than I could have hoped for.

Back to the OP, I've heard of this once before, I think somewhere in my several page thread on M4C about the Core upper that was giving me hell. Definitely annoying but probably isn't a one time thing. Either your ammo has issues or something is going on in your upper, likely in the chamber between the bolt and barrel extension.