Also the brand of cases we use can contribute to higher or lower psi than what John was getting or I get. The data for my load of RL-17 for the 286 Partition was tested by a friend using QL. I told him I was using 64,000 psi as a max load because Tikka was making a .338 Win Mag T3 identical to mine in 9.3 x 62, except with a 2" longer barrel, and, of course, the SAAMI max for the .338 is 64,000 psi. Then the brass must be capable of handling that psi. There was no doubt in my mind that the TIKKA T3 was capable of handling 64,000 psi. My friend tested that load from a 22.5" barrel at just under 64,000 psi = 2619 fps. My chronograph was reading 2622 fps average corrected to MV. That was in using Hornady brass. A correspondent said he couldn't load nearly that amount in his Lapua brass.
It so happens that last year I needed some new 9.3 x 62 cases, and with the shortages only Lapua cases were available (at an extreme price!) in a box of 100. And what that correspondant said, I've found to be true. I'll have to cut back my usual load of RL-17 in Hornady cases by 3 -4 grains in Lapua with its thicker and heavier cases. And that will, of course, significantly reduce MV.
