.300 Blackout pressures

[Lonegun1894]

Does anyone have any idea what kind of pressures the .300 BO generates, especially when using subsonic loads? My main interest is subsonics, but just in case, any idea what the pressures also run in supersonics? Have a hair-brained idea and want to make sure I don't do anything dangerous.

[wlc]

IIRC the SAAMI Max pressure for the 300BLK is somewhere in the 50-51 thousand PSI range. According to Quickload the load I will try next with 5744 generates a theoretical 32,000PSI chamber pressure (sub-sonic load). Hope this helps.

[Lonegun1894]

Thanks, WLC. I wasn't expecting 50-51K. I have a .300BLK barrel for an H&R handi-rifle, which is supposed to be on a SB2 (rifle) frame, but have an extra SB1 (shotgun) frame. Here's my idea, since I tried the two for fit and they fit well--not that that means that this is a good idea, or safe. If the SB1 is safe with .357 Mag and .44 Mag, then if I keep the .300 BLK loads in those type of pressure ranges (sub 40K), I should be safe. And the SB1 used to be sold as a .30-30 and .45-70, not just as a shotgun as it is nowadays. But like I said, hair-brained ideas and all that.

[Jupiter7]

Most the subsonic loads are around 30-35k PSI. This is why they are safe to shoot through pistol rated supressors. Full bore supers run up to 55k psi and can guarantee they have been pushed into 5.56nato territory.

[bikerbeans]

IIRC, the 300 BO data at hodgdon's website lists chamber pressures.

BB

[bikerbeans]

IIRC, the 300 BO data at hodgdon's website lists chamber pressures.

I just checked, the subsonic loads run from <20K CUP to almost 40K CUP

The supersonic lighter bullets 110 to 150 grain run upwards 50K CUP



BB

[Lonegun1894]

That is a great idea, BB. Thank you! I just looked and you got the pressures right. I will check with the other manufacturers and see if or what they list. In the meantime, my first impression is that a subsonic-only gun could be safely put together with a .300 BO barrel and a H&R shotgun receiver if the pressures were kept to 40K or less, and preferably 20-25K. I figure H&R puts barrels in the 40-45K range on these (.357 and .44 Mag), and it is safe, and the .357 Mag and the .300 BO have almost the same base diameter with the .357 being slightly larger due to the rim itself only. I don't have kids so don't have to worry about anyone borrowing it and not knowing to not use supersonic ammo.