Ok to use .457 in .458 Winchester Magnum?

[klover]

Natchez has 405 grain flat nose intended for 45/70 rifles.

I just acquired a Marlin 45/70 (micro) and a CZ in.458 Lott. I am stocking up on reloading supplies, and was thinking to load a few hundred for both rifles.

For the CZ I was thinking to use .458 Winchester Magnum and .458 Lott brass, both loaded mild. The intent is to use consistent ammo for both practice and grizzly defense with affordable boolets.

I was wondering about using gas checks with hard cast boolets for both rifles? I know zero about gas checks.

Big bores are really fun if you can get past the bruise.

 

[highlander 5]

A gas check is just a copper alloy cup crimped on to the base of the bullet. The base is cut smaller to accept the gas check. The Marlin should be ok with a plain base bullet,but the Lott may be a whole nother beast. If the bullets are Lyman No 2 alloy or Linotype you could push them to about 2000 fps with little leading. You may find the Marlin with its microgrove rifling a little harder to find an accuater load but it can be done. 2 thngs that might help.
First keep your loads to around 1600 fps and you should get decent accuracy,this is from the latest Lyman manual. Second try fire lapping the barrel,kits can be had from LBT or Midway. The kits contain a specialized lapping compound that you embed on the bullets and fire in the rifle. I've not used this process in a Marlin but I've used it on several of my handguns and it does help accuracy and keep leading down to a minimum. If you decide to fire lap your barrel do not use any type of valve grinding compound even the finest grit is too course,you'll only ruin your barrel.

 

[Old Grumpy]

I've loaded for my .458 Win Mag for several years, however I have only used jacketed bullets. I use bullets weighing between 300gr and 350gr for general shooting. Most of my loads chrono between 1600 and 2000 fps. I know this is not exactly what you're looking for but I've had good luck loading the big Win Mag by staying within published limits. At 100 yards I am very pleased with the accuracy and you can not argue with the knockdown power it brings to the table.

P.S. I also know what you mean about "getting past the bruise."

 

[Walkalong]

If you pick a bullet that will perform well at .45-70 velocities, then the .458 is easily downloaded to take advantage of that bullet. AA-5744, SR-4759, or IMR-4895 should work in the .458 to match .45-70 velocities.

A lead bullet at 1800 or so FPS is quite viable, with or without a gas check, but the commercial gas check offerings, IIRC, are barely more than plain lead, so I would go with a gas check design. If you cast, that would be a different story.

No reason you cannot pick a bullet to use in both calibers.

 

[bangaway]

Casting your 0wn bullets for .458 guns is a cheap way to shoot. Around here lee moulds are $20 and are 2 cav. Weights are 340 to 500gr. Saw a test on u-tube where 500 gr. bullet a 1600 fps pentrated 36 " more than one at 2000 fps. Did not upset/expand as much. My loads for 45-70 and 458 mag vary from 146 round ball to 630 gr spitzer. 630 is single shot in marlin. Have fun and bangaway.