Semi-Bren fixes

[tankhunter]

I wouldnt worry too much about the bolt face being 'sloppy' with a 7.62mm Round. Remember, the SADF converted guns NEVER changed thier bolts from the .303" Versions.
They did obviously change the extractors, due to needing a longer claw to gript the cartridge canilure.

if at all possible. get a standard full auto gun at a range. Put a spring balance on the cocking handle & JUST begin to pull the springs rearwards.
Then put the balance on the cocking handle of your own gun & repeat the above procedure.
Check the spring pressures. & that should give you an indication of how much you need to
reduce the spring pressure on your gun. It would be a simple matter to clip off one coil at a time, to reduce & check. Reduce & check.
A bit of a ball ache & slow. BUT, you are doing it under a controlled manner! Better to slowly reduce, than cut off too much. & if you dont have a spare spring. You will be in the Shi.....Er, Soft stuff up to your neck!

EASY to do in this manner & you can see your work creeping forward. To a positive result!