SIGforum
James Reeves interviews FBI ballistician about optimal 55.6 barrel length.

This topic can be found at:
https://sigforum.com/eve/forums/a/tpc/f/630601935/m/9850046125

August 23, 2026, 10:15 PM
Dwill104
James Reeves interviews FBI ballistician about optimal 55.6 barrel length.
quote:
Originally posted by Jupiter:
quote:
Originally posted by Dwill104:
quote:
Originally posted by sigspecops:
I just back from the range shooting a 10.5in 5.56 and a 10.5in .300. Neither is suppressed and the .300 had a 150 grain supersonic round. The difference in noise and concussion was very noticeable. The .300 produced less of each. If I had to shoot indoors without hearing protection or a suppressor, I’d would definitely reach for the blackout.


I don’t think anyone disputes that subsonic .300 BO is a lot quieter than supersonic 5.56 out of a short barrel.



Where exactly is sigspecops comparing a subsonic .300 BO to a supersonic 5.56?


sigspecops, the thread below would be a good place to share your findings.

https://sigforum.com/eve/forum...0601935/m/9460077125


Sorry, I misread the 150 grain as subsonic instead of supersonic.