Getting acquainted with the .256 Win Mag

[pertnear]

About a year ago I was lucky enough to buy a custom Martini Cadet chambered in .256 Win Mag. My first loads were with Sierra 87 gr bullets with IMR4198. The little rifle has a 22" straight, 3/4" dia. barrel & my starter load grouped 1/2"! Yes, I'm excited! Unfortunately I only had a small amount of that powder. I have some H4198 Im going to try next. Unlike more modern cartridges I could not find a lot of load info with various bullet/powder combo's for the little cartridge. Any powder & bullets combo's .256 shooters might recommend?

 

[Ropemaker]

About a year ago I was lucky enough to buy a custom Martini Cadet chambered in .256 Win Mag. My first loads were with Sierra 87 gr bullets with IMR4198. The little rifle has a 22" straight, 3/4" dia. barrel & my starter load grouped 1/2"! Yes, I'm excited! Unfortunately I only had a small amount of that powder. I have some H4198 Im going to try next. Unlike more modern cartridges I could not find a lot of load info with various bullet/powder combo's for the little cartridge. Any powder & bullets combo's .256 shooters might recommend?

Years ago I did some load development for the 256 with RP and Hrn 87 spitzers for IHMSA steel in Contender. Found IMR 4198 & Rel 7 both worked well. Tried WW680 and was the go to powder. 10" barrel probably made the diff. WW680 data was from WW load data in product manual as starting point. WW680 is no longer available, but A1680 is supposed to be the same. Other powders MIGHT work is A5744 or LittleGun, no idea as where to start.
Hornady '67 manual has loads for both rifle and pistol (Marlin m62 & Hawkeye) with 4198 as slowest powder for both. Rest are mag? pistol powders, h110, 4227, 2400.
Don't know what intended target you are attempting, but 75 gr HP shoot just as well w/680 as 87's. Wasn't best choice for steel, but hearing the clang at 200 yds on ram was satisfying anyway.