reloads for the bren

[ActionYobbo]

So was the problem that the cases were being rammed home or forced into the Bren chamber and therefore very tight to extract?

Hard extraction shouldn't actually be a problem on a Bren because there is a VERY effective primary extraction process during the unlocking phase of the Bren Gun action. It is sooooo slick that it should unhook anything. Won't explain it here as it is quite complex - unless anyone really wants/needs me to

I think it was the cases and possibly to some extent the powder
I made some dummy rounds and was in the process of testing function and trying to work out the problems. I let the working parts fly forward stripping a dummy round from the mag and when I tried to pull the charging handle back to eject the round it would not move. I tried unlocking the barrel to release the pressure on the locking shoulder so the bolt would move but it still stayed locked in place. I could not pull the barrel off either.
I ended up with the gun on its butt with my foot on the charging handle applying pressure while hammering on the end of a rod inserted into the barrel so it was pushing the round out. Now If only I had relocked the barrel. When the case came free the I was left holding the barrel and the gun fell over putting a nice mark in the wall.

I think this discovery also explains why the cases were coming out so damaged. I was getting bent rims on some and a very deep ejector mark on others. now looking back I can assume the bent rims were the fatter cases and the deep ejector mark were the standard size cases.

Was it a rim behind rim by any chance? ;-)

yes