Simplest things first... Is the magazine seating and locking into place correctly? Feed lips OK? Is the follower moving normally/freely? Did you try a different magazine? The indentations on the case look like they were made by the locking lugs due to the round being at the wrong angle when approaching the chamber mouth... just my 2 cents... post a follow-up when you can?
You're probably right about the indentions being from the bolt locking lugs slamming up against the cartridge. Also, notice how far the bullet is set back from the cannelure.
As far as I can tell, the magazine is fine. Actually I had three identical Pmags and I can't tell the difference between the three.
I probably should have clarified a bit in my OP. I'm not using a mag to test if I can chamber a round, I'm just putting a round in by hand to see if the bolt will close. It's like the bolt needs several thousands to close smoothly.
Say for example, if I take the lower off my AR and drop a round in the chamber, I can push on the back of the BCG a little and the bolt will lock shut.
On the Bren with a round in the chamber, I have to force the bolt to close either by letting it slam shut or by forcing the charging handle forward.
I was hoping someone could tell me if their Bren bolt will close on a round easily without much force. I'm assuming it will.
I've inspected the bore and chamber as best I could and don't see anything that could be wrong. I'm wondering if the bolt got damaged when it slammed against the cartridge.
