Looking for data using RL15 for the 375 h&h

Go to any reloading manual, start 10% down from max and work up until you find an accurate load. No mystery.

^^^^

This

my approach?
take the middle load from the book, set OAL -0.030 from rifling, if it fits the mag, and see how it shoots!

Norma shows 67-69gr (750ms - 775ms) with 203-B, which they show as essentially identical to RL-15 on their burning rate chart.

I'd usually go to a book before asking online for data. Just couldnt find anything with that bullet and powder combo. And i wasnt so sure about using 203-b data just because noemas book says they are close

I shot some 300 gr PP Woodleighs today, 68.0 gr Reloder 15, 2497, 2502, 2505 fps at 10', 3 shots under an inch at 50 yds with a 4x scope.

No signs of pressure.

Same load shoots nicely with 300 gr PPU RN, but a bit slower (2472, 2476, 2488, 2492).

PPU brass, WLRM primers.

I agree with DELL0ROS posts above...Use enough RL-15 to drive a 300 gr. bullet 2500 FPS and you can't go wrong on Buffalo to Duiker..That velocity is kind to bullets and just performs at that velocity..Ive shot everything with a like load..RL-15 is an excellence choice of powder in most 375 H&H or 375 Ruger rifles...

What Ray said.

Mark

Norma Reloading Data - .375 Holland & Holland Magnum

As has been said, Norma 203-B = RL-15.