What powders do you find best for accuracy? No bullets heavier than the 117 and likely will focus on 87-100 grainers.

H-4350, for all those bullet weights.

IMR4350 will work just as well, and may even shoot a little more accurately with some bullets, but H4350 works through a powder measure quite well and is less temperature-sensitive.

Other powders work very well in the .257, especially Ramshot Big Game and Hunter (and even Magnum, with 115-120 grain bullets). But H4350 is always the first one on the list.

I've had two of them and still have one of them. Either H4350 or IMR 4350 is what I've always used in mine. With my first one I had a lot of IMR 4350 on hand and used that with good results. I seem to always have a fair amount of H4350 on hand now and use that. Same good results.

Mart

The two 4350s are pretty much all that I use, as well.

After 40+ years of loading 'da Bob', if forced to pick just one powder for this range of bullet weights, it would have to be H4350, although I burned lots of IMR4350 before the H-version became available, and it worked very well.

However, especially for bullet weights <=100 grains, I've also used plenty of 4895 (H & IMR) and IMR4064 in this cartridge, and those powders have produced very good accuracy with velocities within 100 fps of that produced by the 4350s. Varget is another powder that I've used in similar cartridges, and I suspect it would produce excellent accuracy and acceptable velocities in the 257 Roberts.

Another vote for H4350.

Thanks John and to all who added input.

I've had excellent results from Hunter, IMR-4350, H-380, and RL-15 in both standard & Better Bobs.

I have had my best accuracy and speed from Hybrid 100v. I have heard that there is some concern over temperature stability of Hybrid 100V, I can only give my experience.

Loaded up max load with 100grain TTSX, sighted rifle in at about 17 degress Celcius 63 F, shot at target a few months later at -2 Celcius 28F, there was no discernible change in where the rifle shot between the two temperatures.

H414 and WW760

I've been using the Rob on and off for over 20 years and have always used H4350... hard to beat as a do-all Rbt's powder.

varget for varmint loads and H4350 for 100's and up

Ive had excellent results with W-760

I got better results with RL19 than IMR4350. I shoot 115 bt's and 117 btsp interlocks in my Roberts.

For Heavy bullets 110gr or over I use H4831SC or RL22.
For 100gr I use W760. Anything lighter I use IMR4064.

Hey Mule Deer and EFW...
How bout sharing some of those loads for the H4350 & RL 15 ?? Using 100 grain Interlocks
I've got 3 BoBs
Ruger UL
Browning Medallion (Micro)
And a SC Model 70

Also have a New Haven Model 70 in .270 Win that really likes the RL15 (48grains) with 110grain TTSX