Originally posted by sigfreund:
Although it’s a common misconception, chamber pressure per se isn’t what batters a gun like the P365. As long as the gun is strong enough to contain the pressure without blowing up, what matters more is slide velocity, and that’s largely dependent upon the momentum force of the projectile due to Newton’s third law relating to equal and opposites.
A simple way of just comparing the momentum of different projectiles is to multiply their weight times velocity, and then converting that figure to “power factor” (PF) by dividing it by 1000.
According to Underwood, both 147 grain +P+ loads have a muzzle velocity of 1175 fps, giving a PF of ~173, which is pretty high. I can’t find their barrel length(s), but even assuming that the MV out of a P365 were down at 1100, the PF would be 162.
The hottest ammunition I’ve measured from my P365 was Speer Gold Dot +P 124 grain hollow point that ran about 1130 fps, for a power factor of about 140. With a PF about 16 percent higher for the Underwood load, I would consider that significant. If the decision were mine, I would be leery of shooting much of the higher power load in a P365, if for no other reason than recoil. That obviously depends on the individual, though.
On the other hand, will the gun handle it? If other guns like the P320 can handle that load without blowing up or failing in a spectacular manner requiring removal of teeth from the slide after the shot, I suspect that the P365 will as well. Underwood would not sell that ammo if that were a common complaint.
As for the recoil, I strongly doubt that it could be worse than firing full power 357 Magnum loads from a revolver with scandium alloy frame. (I did that once.)
What velocity do you get for the load from the Glock 26? And if I could handle the load in a gun like that, I’d probably be able to handle it in P365, especially with a longer grip.
The only way, of course, to answer your question is through actual testing. I doubt that you’ll find many YouTube videos addressing it, so if you decide to do it yourself, please come back and let us know how it turns out.