what size shim do I need?

[Guttertroop]

My STG barrel is overtiming on my DC receiver. I can hand tighten it to about 1:30. What size shim should I use? Alternative ideas to using a shim are welcome.

Thanks,
Gutter

[Arby]

You might try backing off the barrel a bit and then hand-tightening it to 10:30 or thereabouts using feeler gauges. That should give you a pretty good idea of what thickness shim you will need. Try checking it a various points on the circumference of the barrel/receiver in order to ensure that both barrel and receiver are cut square.

It might also be a good idea to check the clearance between the chamber face and inner race of the receiver. I forget what the parameters are for that dimension, but I'm sure someone on the board will come up with a quick and correct answer if you feel the clearance is either too great or non-existent.