TruthTellers
New member
From what I'm seeing with commercial .45 +P the velocity gain is close to 100 fps more in a 5 inch barrel, which is a lot closer to 10% than 4 or 5 percent..45 ACP +P Maximum is right at 10% higher pressure than standard maximum.
There was an old rule of thumb that for SMALL CHANGES you got about half the increase in pressure out as velocity. So +10% pressure = +5% velocity at best. Vihtavouri said more like 4%.
In the case of 9mm +P, that 4-5 percent velocity increase is spot on.