Looking for some pet loads for the .257 Roberts Improved useing 75-117 gr bullets.Probably 75gr V-Max's for GroundHogs and the 100-117gr Sierra's for Mule Deer.....

At the moment Im using 45 grns of IMR 4350 behind a 115 grn BT for 3100 fs. BBl is 24" and accuracy is adequate but it still needs a little work there. Im going to use the ladder approach and bullet seating to refine it a bit if I can ever get the time.

I am in the process of working on a 75gr. V-MAX load for my rifle, so I can't help you there. For the heavier bullets I've tried, the best so far has been the 117gr. Hornady SST over 53gr. of RL-22 for 3080fps out of a 24" barrel. I've never seen this load published so work up from 50gr. or so. I've fired this load 4-5 times in RP 257 cases and the primers are still tight, so I have deemed this load as safe in my rilfe only.
I tried the 100 and 115 Nosler BT, 100 Hornady SP, 115 Partition and the 117 Hornady BTSP also, but the SST was the best so I have settled on it for my deer and antelope bullet. for powders I have used H4831, IMR 4831 and 4350, RL 19 and 22. IMR4350 was the most accurate but slow. RL22 gave me <1" groups with the highest velocity.
Hope this helps,
Elk Country

My rifle like heavy loads of IMR4831 with the 120 Speer Hot Core. Also, the 120 Sierra HPBT is VERY accurate. I found the 117 Sierra's to be accurate, but I got nervous when they would not penetrate mature bucks with a broadside lung shot.



ElkC: how does the SST perform with respect to expansion penetration...any experience, yet? thanks

Alpine:
Although it's been a while, my records show I had very good accuracy with the Hornaday 75 gr. v-max and 46.4 grs. of IMR-4895. My seating depth was 0.010" off the lands as measured to the ogive. From QuickLoad, my 24" barrel shows MV at 3490 fps and pressure at 48331 psi. I got very good accuracy with this load, something like 4 shots into less than 0.4". I'm not used to this kind of velocity & accuracy but that's what my records show. Hope I can continually reproduce these results. When seating bullets, I measure the depth of each round. Guess it's kinda anal but....
Hope this helps some. Bear in Fairbanks