I am working with a Wby Accumark 26" barrel and the 115 Berger VLD's at this point. I do have some 115 Barnes TSX as well to try out.

What powders are useful to pull some speed out of this combo?

I tried h4831 and Fed GM215m primers over the weekend and did have a good load at 67.5 grains. 19 FPS spread and groups were averaging .70" @ 100 yards but was only getting around 3150 fps before mild pressure signs showed up.

I'll take accuracy over speed any day of the week, but I think there might be a better powder to accomplish this.

R25, h1000

IMR 7828 was a laying on of the hands for my 240. Several friends like it too for 257's and 300's. We all get published velocity.

I started a Mk V 257 on Reloader 22 and it does OK. Based on my buddies results, however, I'm going to IMR 7828 when the current loadings are consumed.

So far, IMR-7828 has been best with 110 and 115 gr bullets in mine. I am trying Ramshot Magnum, though.

I have had my best luck with RL-22

Try 7828.

RL 22 in my Wby Fibermark gives me 3700 fps with the 100 gr TSX, along with superb accuracy.

rl22 rl25 rl33

RL-22/MRP (same powder) has always worked great

Thanks guys...Looks like I'll have to pickup some RL22 and give it a try.

Any estimates on velocity with the 115 gr's?

Do you know the velocity on that load? Nice group btw!

I would guess about 3100 fps

I use IMR 7828 69.0 grs and a 117 gr Sierra flat base,it's getting an average of 3258 fps. Oh and a CCI 250 mag primer and 26" barrel.

Another vote for 7828......but, if I was starting over today with the 257 WBY, my first try would be with RL-33.


X-VERMINATOR

Im getting 3325 with a 115nbt from 7828 and 215m from my 257wby.

I never got around to checking the velocity. I tried several powders that included IMR 7828 and H1000 and got the best accuracy with RL-25. I know it's fast enough and I'm much more enthusiastic about getting good accuracy than about getting maximum velocity.

Velocity is critical, especially with actions less strong than the MKV. Here is my go to load:
71.3gr RL-22
F215M primers
Norma/Weatherby brass
MV: right at 3740
100gr TTSXs (but the 100gr TSX and Hornady SPs shoot to POI as well):

Now that is smoking!

That is pretty much the same result that I have with mine. It shouldn't be powders but powder, namely RL22 in any I've worked with. 72 grains and a 100 TTSX is the recipe.

I shoot IMR7828 with both 100TSX (72) and 110AB's (71).

24" SUB MOA Vanguard, I get 3500+ with the TSX and 3400+ with the 110AB.

I have a few .3s with the AB and many in the .5 range with the TSX.

Tony