Barrel Extension Separation!

[1075 tech]

The way I understand this, either the pin was sheared or was too short and never was properly fitted locking the barrel and extention together. Which was it?

In my case, the indexing pin was never in contact with the barrel threads. I have heard both that the indexing pin is supposed to go into the barrel and that it is only for indexing into the upper, not for securing the extension to the barrel.