Yes, the old 270 grain round nose .375 bullets are a bit stiff in the jacket for the 2 1/2" velocity.
They need the same treatment as I described in the Fraser thread - or just make them soft nose splits
to enable the bullet to mushroom, just like they did in the old days.
The .366" bullets are the same - they're constructed for 9.3 x 62 and 74R velocities, not 400/360 or 360 x 2 1/4".