Originally Posted by
Treiz
Just returned from a function test and zeroing my bcm BFH LW 16" middy upper. The lower it is mounted on was upgraded with an A5 kit, A5 spring and swapped in the A5H4 buffer. I found that this combo would lock back on XM193 55gr. Of course ymmv
I was surprised it locked back with as much force as it did. I have all the A5 buffers thinking that I would start with the A5H4 and step down until it functioned, but it ran right off the bat with the heaviest buffer. I'm just not sure where to go from here.
EDIT: I checked my ejection chart, brass was hitting between 3:30 and 5, so it may have been short stroking slightly. As I said it didn't have any trouble locking back that I noticed. I'm going to clean it up and try again with the A5H3 and see where the brass ends up.