I just ran the numbers for the .220 Howell with a Pmax of 63000 using the 75 Amax out of a 24" barrel and I got a max MV 3464fps and 63Kpsi.
With a Pmax of 50K QL showed me a max MV of 3250fps.
So according to QL anyway it appears that 200+fps would be gained from a 13K increase in pressure.
Just some cogitating on my part and I fully realize that 50Kpsi max was part of the design parameters for this cartridge.
