mcb
Member
@mcb , can you provide more details on that load? Does it cycle the bolt? What powder and charge weight?
It looks like your upper has a 20" barrel. I cut mine down from 20" to 12" and might need to open up the gas port to get more gas heading rearward for subsonic loads. Perhaps an adjustable gas block is in my future. I shot some 360gr gas checked bullets this weekend using 15.0gr of Trailboss which results in a MV of around 1,100 fps but not enough gas to cycle the bolt. That load supposedly generates about 36,700 psi but with such a short dwell time there's not enough gas going down the gas tube.
Without getting this thread too far off topic I hope you don't mind if I post a link to another forum where I created a thread with a fairly detailed write-up of the workup for my subsonic 450BM load: http://450bushmaster.net/viewtopic.php?f=5&t=15365