The maximum load with IMR4895 listed for the 270 TSX in the Barnes #4 manual is 73.5 grains.
Hodgdon lists a maximum load of 66.0 grains with the SAME bullet and powder, at 49,500 CUP--which converts to almost exactly 60,000 psi. So the maximum Barnes load is well over 60,000.
Unlike many of the larger British cartridges of the era, from the beginning the .375 H&H was loaded to 55,000 to 60,000 psi, about the same pressure as the .30-06. (The only exceptions were "tropical" Cordite loadings, and the flanged version for double rifles.) The SAAMI maximum average pressure for the .375 H&H is 62,000 psi, despite all the older rifles chambered for the belted round.
