I don't know what an original High Wall can handle, but I do know they have been chambered for all manner of modern cartridges. Having said that, it sounds like he might be pushing the envelope. Do you know how many grains of 4198 your friend is using? My Lyman manual shows up to 48 grains of 4198 with a 500 grain bullet, but I found that a reduced load of 45 grains sent the 500 grain projectile down my 34" barrel at 1880 fps! Talk about a hard wallop on the shoulder - that was pushing the low end of .458 mag levels! No extraction problems or any indications of high pressure, but it just wasn't a fun load - especially with the curved steel butt plate.
I've since developed a load of 40 grains of 5744 behind a 325 grain Hornady FTX bullet that seems to be quite accurate, and relatively gentle to shoot. There are plenty of good, gentle smokeless loads you can shoot in your .45-90 High Wall.
I've since developed a load of 40 grains of 5744 behind a 325 grain Hornady FTX bullet that seems to be quite accurate, and relatively gentle to shoot. There are plenty of good, gentle smokeless loads you can shoot in your .45-90 High Wall.