That can't happen.
I have been having some issue with a host gun having some failures to eject. It had a broken extractor and all I could get at the time was a made in the USA extractor and was wondering if it was causing the ejection problem. So I took a bolt off another gun. But still had the every other mag or more failure to eject. Was going to swap the parts back when I noticed this mess. Now wondering if the carrier was cracked all along or if swapping the bolts did this? And now the locking piece wont come out. It turn freely and firing pin moves as expected but it wont separate from the carrier. What have I done?
That can't happen.
Is anything broken off and loose inside the carrier? Have you tried wiggling the locking piece in and out while you rotate it? There shouldn’t be anything that can prevent the locking piece from coming out if it can rotate.
Is that a German BCG?
Let's go in the opposite direction. Can you push the locking piece in and rotate it 90 degrees counter clock-wise?
Pushing it in it turns freely. It is only when trying to pull it out the hole there is resistance. I wrapped it in electric tape and used a pair of vise grips to pull to out. It took about all I had to get it out
Did any bits of metal come out when you managed to extricate it? What does the locking piece look like?
When you push LP in and turn it the little grooved nodule on the side of the locking piece should engage the
small wire you see thru the hole in the side of the bolt carrier. You can see it in the pic you posted of the bolt
carrier. The locking piece should snap on to the wire and lock into place with the 90 degree turn. It should not
slide over the wire and keep turning.
Just out of curiosity what weight / brand ammo had you been shooting?
No matter the cause, I can’t imagine what would cause the carrier tube to crack like that. It just floats freely in the receiver.