Chronographed some loads today:
Win M70 24" barrel .375 Ackley improved
270 grain Failsafe bullet
IMR 4350 powder
Winchester fireformed case and magnum primer
2 rounds of each load

grains:fps
81:2525
83:2614
85:2603
87:2705
88:2692

Velocity less than anticipated. No excessive pressure signs. Cases cool coming from chamber; odd. The 87 and 88 grain loads were compressed.

Impossible to beat Re-15 in that chambering,utilizing that projectile weight,in my opinion.

That when weighing speed and accuracy potential..............

Even Parker said that he doubted that any "Ackley Improved" over .30 caliber makes no difference...

I'd be suprised to learn that P.O. was privvy to Re-15................(grin)

It seems that we need a faster powder.

What do you think?

I think Re-15 was THE propellant of choice in the five 375H&H's I've had,as well as the two 375H&H Ackley's. The 235-270X's my favored projectiles in all,though I've dabbled with the 270FS and found it to be a very good bullet too.

RE-15 is very good stuff,in those applications,in my opinion. Your mileage may vary............

My .375 Improved did 2670 fps with 85 grs of imr 4350 and the 270 Hornady in it's 22" bbl. This rifle was a mistake but now I know better. No more improved cartridges and no more Sako's.

The .375 H&H has enough capacity as it is. Better to get a .416 if you need more power and can stand the kick.

You might try Varget......I like RL15 but the lot-to-lot inconsistency drives me nuts. Plus Varget doesn't vary much with the temperature.