Does anyone have a recommended powder to try with 260gr and 300gr Accubonds? My rifle is a custom Brno 602.

http://www.accuratereloading.com/375wby.html

Provided by forum member RIP

That is old info, but still good.
Since then I discovered H4350 Extreme, made in Australia and imported by Hodgdon.

That will give best accuracy and highest velocity for pressure with 300-grainers, you can duplicate factory loads, for 2800 fps in a 26" barrel with the right bullet.
Aim for 2740 fps in a 24" barrel.
Start at 80.0 grains of H4350 and work up.
It is a "Short Cut" powder, easy to meter,
and is the most heat-stable/temperature-insensitive of any you will find,
for the .375 Weatherby.

You can get excellent results with 260-grainers and H4350 also. Top out around 90.0 grains H4350 with 260-grainers.

RL-15 and Varget can be used with the 260-grainer.
You will not equal the velocities of H4350, however, until pressures are excessive.
Max loads with those powders will be less than 80 grains.
Decide based on accuracy in your rifle.

I dissected the factory .375 WBY load by Norma.
It contained 88.5 grains of a powder which looks like/I guess to be Norma 204, used with the 300-grain Nosler.
Seems to be close to a 100% load that truly delivers the claimed 2800 fps in a 26" barrel.

By handloading, you can do better with H4350.
Better accuracy and equal velocity.
Fine tune the powder charge and the COL with the desired bullet in your rifle.
Powder lots and rifle throats may vary.
Your mileage may vary.
Don't blow yourself up.

DRG says: "Kiss my liberal grits!"

Thank you very much RIP, much appreciated!

BTW, what is a good fireforming load to use for H&H brass?

Thanks

I do not do any pistol-powder-and-filler fireforming.
Use any normal .375 H&H load.
If you are loading them, get the cheapest jacketed bullet and the desired brass for plinking & fireforming loads.

The .375 Wby max brass length is 2.860", trim to 2.850".
You will be a little short with .375 H&H fireformed, but it works fine, no worries.

I much prefer getting Norma-made, properly headstamped brass for .375 WBY.
It has larger case capacity, and is of best quality.
It is required to get top velocities within pressure limits.

When you get your maximum .375 Weatherby 300-grain load finalized,
try this:
Zero it 2.5" to 3" high at 100 yards.
Then "fireform" a standard .375 H&H 300-grain factory load at the same target with no scope adjustment changes.
You will find the .375 H&H 300-grain factory load is hitting very near dead-on at 100 yards,
with good accuracy.
This is handy in a pinch,
if you get separated from your .375 Wby ammo.

The standard 2500-2550 fps H&H velocity will also have been slowed down to about 2400 fps.
You might notice gentler recoil than a standard .375 H&H too, if your recoilometer is sensitive enough.
You now have transformed the standard factory .375 H&H load into a slowed-down-super-killer, according to "Doctari."

Actually slowing it down is helpful only if using a lousy bullet that cannot stand higher velocity.

DRG says: "Kiss my liberal grits!"

You can also use 416 Remington brass...it ends up closer to the 2.850" length after necking down and firing.

But I agree with RIP, I bite down on a willow stick and buy the Weatherby brass. It lasts a long time and is tougher than Remington brass, as well as having more volume.

I'll play second fiddle to RIP here..........he definitely knows his .375 Wby crap.

Try a few rounds of 260 gr. loaded with H-414. I've found it to be a stellar performer with mid-weight bullets.

Many thanks guys!

I have to agree, for the Weatherby's to perform at their best, get the quality Norma/Wby stuff. Personally I buy the Weatherby, as its MADE by Norma lol but like 15% cheaper then Norma brass. Go figure.

IMR 4350!!