Locking Shoulder question

[Longshaor]

At the risk of sounding a complete moron, what is the reason for the different sizes of locking shoulders and how do you know which size you need for a particular Bren?

Cheers!

[browningautorifle]

It has to do with the headspace. If it's too large you have separated cases. If too tight it won't close. You will need headspace gauges to determine the correct shoulder.

[Longshaor]

OK, thanks Jim!