I am going to try some 120gr Sierras in my Vanguard. Does anyone here use these? If so, what powders do you use? Also need start/max load specs if you have them. I have H-100, 7828, RL22 & RL25, and Retumbo on hand. My Sierra manual doesn't list any of these powders for this bullet, but was hoping to hear from someone who has used one or more of them successfully.

I have loaded 120gr Nosler Partitions and Swift Aframe bullets. The rifle is a Ruger M77 with a Douglas SS barrel since my daughter shot out the original. I tested a bunch of different loads all at the top end for hunting South Africa PG next year. This will be her rifle on the hunt. The very best load was 47.5gr H-450 with a MAG (win) primer, Swift 120gr A-Frame bullet. Put 5 rounds into one hole with a ave of 2899FPS. When I used a standard primer the groups opened up to 4+ inches.
Other loads tested include, all mag primers, all 5 shot groups:
IMR4831-45grs--2858FPS ave-- SD11-Nosler Par-Very good accuracy
RL19-48gr--2801FPS ave--SD10-Nosler PAR-ok accuracy
H-450-47.5gr -2916FPS ave-SD14-Nosler PAR-one hole group-super excellent
IMR4350-44gr-2873FPS-SD11-Nosler PAR-Ex group I pulled 1?
IMR4350-43gr-2803FPS-SD7-Nosler PAR-good group
IMR7828-47gr-2854FPS-SD16-NoslerPAR- ok group
RL22-47gr2751FPS-SD9-Nosler PAR-ok group

These loads should be fine with your bullets. I have not tested any with your bullets as I am not a fan of them. In the 257Roberts I only shoot Nosler and Swift bullets. I usually shoot 100gr but decided on 120 for Africa as my daughter wants to shoot a Kudu.
All brass was trimmed to uniform size,chamfered inside and out, was new brass,primer pockets uniformed and inside flash hole deburred,weighted into groups within 1 gr each and the necks run thru my sizer die to be sure they were uniform round. All primers were seated with a hand primer(Lee).

Hope this helps.

Is that load data for a .257 Roberts? Those are way low charges and velocities compared to what I use in .257WBY MAG.

Garry,

I'm sure Retumbo would be ok but I have not used it. I know RL22, RL25, and H1000 will work well in .257WBY with 110-115gr bullets. I have not shot the Sierra bullet you are asking about but using Alliant and Hodgdon websites found start loads for all the powders you mention.

Yes it is for a 257Roberts. I have data for a 25-06in a Ruger M77 and 257Weatherby in a Vanguard also. If one of them is what you are looking for let me know.

Check the Hodgdon site for IMR 7828 data.

Any of these should do. I won't give you data because my gun is a short throat custom using coated bullets but if I could only pick three to try it would be RL25, H1000, and IMR 7828SSC.

Thanks all. I decided to try the RL25 first. Loaded 5 each starting at 66 gr. and worked up in .5 gr. increments to 70 gr. I've only had the time to try the first 3 loads so far, but all are showing promise, with no sign of high pressure yet at 67.5 gr. and groups just over 1". Next time at the range I will test the rest of them. Hopefully I'll get lucky and find the right load in there somewhere.