Cast bullets in .458 WM?

[smokemaker]

I tried some 420 grain hardcast .459 gascheck bullets in my .458 Winmag Interarms Mauser Mk 10, using 20 grains of Unique (Max allowed 22 grains). The gun sprayed all over the paper, with the bullets tumbling badly. The load shows maybe 1400 fps... maybe too slow to stabilize? The gun shoots factory 500 grain soft points into 2" at 50 yards with iron sights. I'd really like to shoot cast bullets in this gun, as jacketed bullets and especially factory loads are really expensive. I drive the same bullets out of a Winchester 1886 in 45-70 doing around 1800 fps and it's a real tackdriver. If anyone has any suggestions I'd really appreciate it.

Jeff

PS: the moderators may want to move this to reloading as I am a nitwit.

 

[ken grant]

.458

The reason your bullets are tumbling is because they have to make a long jump to engage the rifling. The .458 has a very long throat. To seat the bullets out so they don't have to make the long jump in most cases means the cart. won't fit into the mag.
I found that using a slow burning powder will work better in this case.It starts the bullet out much slower and doesn't slam it into the rifling as a fast burning powder does.
I have even used H4831 compressed loads and got good results.

 

[RecoilRob]

Yes, if they are tumbling they are not stabilized and probably need more velocity.

In 45-70 I use RE-7 with satisfaction. You might try something other than the Unique that will boost the speed a bit.