Originally Posted by Tiff
Yep its just a necked down .338 Lap Mag case. I think I will follow all of your advise and start at 97.0 grains and work up until I reach pressure. Then back it off a bit (is only 50-60 F at the moment) so I don't hit pressure when it warms up....if summer ever does arrive!
Just ran the numbers in QL.
Using the standard case volume of 102gr, Sierra 240gr MK seated to a cartridge OAL of 3.7", and 97gr of US869, using 3625psi initiation pressure, the supplied case weighting factor of .55, and a guessed 26" barrel, resulted with 2832fps and a max chamber pressure of 64981 psi. The listed max pressure for the 30-338 Lapua is 63817 psi, so you might want to back off a little more. 94gr shows 57.7Kpsi, and that might be a better place to start! This was done with the Temp setting on 70 deg, but adjusting it down to avg 55 deg, the pressure falls to 63Kpsi, which is right under max listed pressure.
If you want to run the numbers yourself, send me a pm and I'll give you the QL info for US869.