Thread: Noise level of subsonic calibres

Originally Posted by sixtus

Ok interesting. But I think all else being equal 38, 45colt and 44 magnum subsonic, say pushing them to 1000fps, you can always get lower pressure as they are bigger cases for their calibre. Checking hodgon reloading data and 38 sp are running about 17000PSI max, 45 and 44 can be running as low as 14,000PSI, the 45acp is 20,000PSI with factory. Will it still be quieter? My only experience is 38/357 so I cant compare ito the others.

The figures you see online are a measure of chamber pressure not muzzle pressure. The 20k psi of the 45acp is only within the confines of its little case.

E.g. 300 blackout and 308...

The blackout with a much smaller case will create much higher peak pressure (accelerating the bullet very nicely), but with less powder there's less total gas volume and by the time it's expanded all the way down the barrel, the will be very little muzzle pressure. Exhibit A:



308 with a much larger case, needs more powder to generate enough pressure to accellerate the bullet. Chamber pressure might be lower, but the extra gas created by the powder results in more pressure at the muzzle. Exhibit B: