I’m in the process of planning out a 300blk build and need a little help with the buffer system.

A little background on the build: I’ll be using a 8” or 8.5” BA barrel. Is there preference between them? Here in NJ suppressors are banned so it will be shooting supers 99% of the time, only occasionally shooting subs when I’m out of state. Eventually when I get out of this state, it will be a dedicated suppressor gun.

I’ve really enjoyed the A5 system on my 11.5” 5.56 and would like to use it again here, if it makes sense. What spring/weight combo would be most effective for supers, unsuppressed? For way future reference, what do people use for subs, suppressed?

Standard spring and H2 is typically a good starting point. A lot will depend on the ammo, but supers are not particularly finicky. Same with suppressed subs. Maybe drop to a carbine buffer if necessary but always try it first. A lot of people fiddle with hardware when no fiddling is necessary.

Unsuppressed Subs are usually the stories you hear about.

I just built a 300 using the 8" BA barrel. It has run flawlessly with 125g supers (1920 fps) and 220g subs (1050 fps), suppressed and unsuppressed with an H buffer and standard spring. It also worked fine with H3 buffer/standard spring and A5H2, but I only tried it suppressed. The barrel seems to be gassed appropriately.

Like Obsessed said, I agree the issues seem to be unsuppressed/subs. This would be likely worse with longer barrels and lighter bullets.

My 8.5" BA barrel runs fine with a standard spring and buffer.  Brass ejects to 2:30-3:00 with supers.  IMO each barrel is an individual, get a standard spring and a couple buffers around the H weight (or the KAK tunable buffer) to find which combo your barrel likes best.

I ran a standard buffer on my original 8.5.    If you have a Law folder, remember, that adds mass as well.

Awesome. Thanks for all the input.

Standard buffer and spring... zero issues.