Steve - must have been a 'slow' barrel. Perhaps my .375 is a 'fast' barrel, but then so is my 9.3x62 (an improved case) and my first .375/06IMP as well.

Yes you are right about ti's design, of course, the Brown/Whelen is very similar to the 8.5x63 - Ackley himself declared the Brown/Whelen to be one of the best as it actually duplicated the .358 Norma Magnum factory ammo - 2,700fps+ using 250's - with a .30/06 case. That makes the 2,650fps with 250gr. for the 8.5x63 as being quite believeable, long with the rest as well.

BTW - the .338/06 & IMP suffer from too-long a neck, which reduces case capacity more than necessary.

I am a firm believer in long barrels - 24" to 25" is 'good' for me.