Thread: OAL effect on pressure and velocity

So I set out to get a load sorted for my 9mm pistol. I have been shooting Belmont Factory ammunition for a while to collect the brass. Have had excellent accuracy from them, so I decided that matching them would be a good place to start.

I had a pound of AP70N to use ( will have to change in the future) and went to book minimum load with the same overall length as the Belmont Factory.

124gr CMJ RN - 4.3gr AP70N - 1065fps - 132pf (book says 1035fps)

I would like to get 130pf with as little powder as possible (2\10ths of a grain = 100 extra rounds per pound approx).

I have been advised that if I drop my load by 4\10ths of a grain, and reduce my OAL a bit, I should be able to get the PF I want, as the reduction in OAL should increase pressure

Anyone have any experience with doing this? Pistol is a CZ75 SP-01 Shadow so has a 4.5" barrel.