TTK Ciar Posted January 14, 2021 Share Posted January 14, 2021 I have read claims on other forums that the US Army has had the manufacturer adjust the propellant used in M855A1 so that its chamber pressure is 57,500 psi, down from 62,000 psi. Some quick Googling failed to bring up a reputable source confirming this, but my Google-fu is known to be deficient. Does anyone know if it's true? Link to comment Share on other sites More sharing options...
shep854 Posted January 15, 2021 Share Posted January 15, 2021 I wouldn't be surprised; the round is rough on barrels. 62k psi is approaching proof-load pressures. How performance is affected will be interesting to see. Link to comment Share on other sites More sharing options...
EchoFiveMike Posted January 15, 2021 Share Posted January 15, 2021 62k psi is meh. Do the math for bolt load. I'm on a phone, otherwise I would. Match shooters fairly consistently run 75 and 77gn projectiles at 2800-something from 20inch service tubes. Primers don't start to go away until 70k plus. I used to run 69 SMKs at chrono'd 3040fps, with no pressure signs, just change bolts every season as a precaution. That said, I've heard nothing about it. It seems stupid, so it might well be true. S/F....Ken M Link to comment Share on other sites More sharing options...
Simon Tan Posted January 15, 2021 Share Posted January 15, 2021 Dump the carbine length. Forget mid. Go full bore rifle on a 16. Use can for dwell. Link to comment Share on other sites More sharing options...
shep854 Posted January 16, 2021 Share Posted January 16, 2021 23 hours ago, EchoFiveMike said: 62k psi is meh. Do the math for bolt load. I'm on a phone, otherwise I would. Match shooters fairly consistently run 75 and 77gn projectiles at 2800-something from 20inch service tubes. Primers don't start to go away until 70k plus. I used to run 69 SMKs at chrono'd 3040fps, with no pressure signs, just change bolts every season as a precaution. That said, I've heard nothing about it. It seems stupid, so it might well be true. S/F....Ken M Thanks! Link to comment Share on other sites More sharing options...
Wobbly Head Posted January 18, 2021 Share Posted January 18, 2021 How are they measuring this as it brings up the whole 7.62x51 vrs .308 issue as the military use CUP PSI measuring and SAAMI piezo measuring standards ? Link to comment Share on other sites More sharing options...
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