Another BREN-fan (introduction)

[erik3D]

I've never reloaded .303 Britsh, so I wasn't aware that this calibre was designed to use berdan primer cups with such a large diameter (and thickness!).
The berdan primers I'm to used were for the likes of 7.62x51 and 7.62x39, and a LOT smaller.
No wonder then that the 'bite mark' the BREN ejector makes sits so close to the edge of the primer pocket!
I've redrawn my .303 case model to better show its true dimensions.

Also, given the 0.79 mm base thickness of that primer, it's no wonder those semi-auto conversions need a very powerful striker spring to make things go BOOM.

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.

[erik3D]

Here's a section view of the BREN the instant the ejector hits the cartridge case after firing, unlocking, and extraction.
I've drawn the piston post buffer spring at maximum compression, but I'm not sure exactly when it reaches that position (if ever), and/or for how long it remains being fully compressed.

[erik3D]

Still searching for an angle to show relevant details of the mechanism (maybe for an animation of a firing cycle). It's not easy to find a good one.

Looking at it like this it seems a small miracle those cartridges manage to find their way into the chamber : )