I have been considering buying a CZ 550 chambered in 458 win mag and having it chambered to accept 458 Lott as well . I see from some of the other posts here that this is a relatively popular thing to do, so I imagine some of you can answer my questions regarding this conversion .

Is this just a simple matter of a gun smith running a reamer down the barrel and lengthening the chamber or is there more to it? How about the feed ramp and magazine, are any changes necessary. Will it reliably work with both 458 win mag and 458 lott after the re-chamber ?

Finally is accuracy significantly effected for the 458 win mag after the rechamber since the bullets will have to "jump" a fair distance to the rifling? Thanks.

Don't know about the 458 Lott but my 450 Ackley (CZ 550) required quite a bit of work to make it feed reliably. The 458 Lott should be a little easier to make it feed in the CZ 550 but it still needs some work.

Also, nobody in their right mind would want to shoot the 458 Winchester in a 458 Lott rifle on purpose. It means to be used in an emergency situation. You can always downlood the 458 Lott to suite your needs. Good luck.

Not shoot 458 Win Mag loads in a gun chambered for the 458 Lott ? Why not ? That versatility is one of the big selling points for doing this conversion (at least for me)- still be able to shoot less expensive 458 Win Mag ammo. Kind of like 38 Sp in a 357 Mag or 45 Colt in a 454 Casul or any other of several examples. Does it not work that way?

I had to file off the part of the rails and the ramp to get it to feed. The problem is that if you go too far, it's a piece of junk and you have to start over again.

Also I had to grind away some of the ridge/shoulder (I don't know what it's real designation is) off the front of the bolt since it was keeping the cartridge heads from slipping up underneath the extractor when fed from the magazine.

Its not a good idea to shoot 458 Win in 458 Lott guns as it will cause excellerated throat erosion. That is a well known fact, but many folks do it on a regular basis...also it is your gun and your priviledge....but the advise given was warranted advise IMO...

Thanks for the replies.

BTT