What are my choices when it comes to .510 rounds that will feed through a cz550's magazine? I was going to convert a .416 rigby to something based on the 460 weatherby case, but I want to know what I'm getting into. Hard hard is it to get to feed properly? Is a cartridge available that will feed long target style bullets from the magazine? In all the references I see the rounds are single loaded. If I have a cartridge that is short enough to feed, will the bullet travel fast enough to be stable? Am I wanting to have too much? Perhaps I should be lucky to be able to make a rifle that feeds at all with any bullet.

Kirtan

Kirtan,
I am certain you'll get a ton of posts in the matter, but the fact is you'll be able to convert the 416 cz to any of the 500/510 stuff, A2, wells, etc. You might (RGB?) be able to stuff in a jeffery or a gibbs.
the www.470mbogo.com is based off the 416, and you can find out tons of details on his site.
jeffe

If you want a repeater using the 50 bmg bullets, then you'll need to go with a shortened case, I'd have to measure the bullets, but something in the 2.25" range. As far as what can be fed through the 550, you can go with a 460 variant, 510 wells, 500 A-sq, etc, a 500 Jeffrey, 500 AHR (non-rebated slightly longer necked Jeffrey) or a 510/505 Gibbs.

With the shorter cased rounds made to fit the mag, I'd gueess you'd be giving up 200-300 fps, so say 1800 fps at the muzzle. So long as you use a fast twist barrel 1-10, you should be fine. I'm curious to see if my long throated 500 Jeffrey will stabalize the bmg pills from my 1-15 twist tube.

Most folks building these set them up as 50 cal sporting/hunting rifles first, and just have the long throat as a bonus to allow single shot plinking with the 50 bmg pills.

If you start with a good CZ550, you can get any of the .510 rounds or even a .505 Gibbs to work with very little problems. this includes the 500A2, 500AHR,.510 wells ,500 Jeffery etc. Your limitations are the bolt face and the absolute need for a second recoil lug on the barrel ( don't even think about such a gun without one. You then have do deal with the stock issue. Figure on spendind $1500-$2000 for the conversion.-Rob