380 Auto Frangible

[madlink]

I have worked up a load for 75gr frangible bullets in 9x17 (alias 380 Auto), but I am not satisfied with the muzzle velocity. My prescription is:

- 75gr frangible bullet

- 3.4gr Bullseye powder

- Winchester WSP primer

The resulting muzzle velocity from Kel-Tec P3AT is about 930 f.p.s., for a "power factor" of about 70.

But the puzzling thing is that, even though 3.4gr Bullseye seems to be every manufacturer's top safe charge, I have used commercially available ordinary 380 Auto ammunition that gives "power factors" of 90 or more. Of course that's with a 95gr bullet.

So here's my question: Can I safely increase the charge for the 75gr frangible bullet up to a power factor of 90? The charge of Bullseye powder would probably have to be in the ballpark of 4 grains or more.

[anachronism]

Try a slower powder. 231 looks promising.

[madlink]

Why would a slower powder help? Wouldn't there be less gas to propel the bullet? Perhaps all the powder won't even finish igniting before the bullet leaves the muzzle.