What are the differences in the magazine box between a CZ 550 in .458 WM and one in .450 Rigby?

Thanks!

A second question can be added:

Can the CZ 458Win be rechambered into the 450 Rigby along with altering the same magazine? Or must a new magazine box and bottom metal be purchased?

(Bolt face, bolt stop, and rails need to be altered, too, of course.)

Big diclaimer, not a gunsmith, just reverberating what I "think" I've read. I think, with the shorter body of the 458 win, you could drill out the throat to the Rigby case, open up the bolt face, swap the mag box for a Rigby box and clean up the rails/feeding and it should work.

Now, hopefully a real gunsmith can chime in on this.

quote:

Originally posted by Philip A.:
What are the differences in the magazine box between a CZ 550 in .458 WM and one in .450 Rigby?

Thanks!

Here is the ribbed "375H-H" box (modified by a soldered-on, front-of-box reinforcement of the sheetmetal by Rusty McGee)
that the CZ-USA Custom Shop uses in their 450 Rigby rifle:



This box worked best in the .375/404 Jeffery Saeed of 2012. I tried both it and a reinforced 458WM box, along the way in Rusty McGee's feed job.
The original 404 Jeffery from CZ came with this box:



The sheetmetal box that CZ uses in the .458 Winchester Magnum and the .458 Lott rifles is the "458WM" box.
It is the same except smooth-sided, without the ribs stamped into the sides of the box.

The ribbed one is stamped "375 H-H".
The smooth-sided one, with greater internal capacity, is stamped "458 WM"
to distinguish the two different boxes used in the CZ 550 Magnum rifles.

I have observed the 375 H-H/ribbed box is used in these chamberings of the CZ 550 Magnum:

.338 Lapua Magnum
.375 H&H
.416 Rigby
404 Jeffery
450 Rigby
.505 Gibbs

I have observed the smooth-sided, "458 WM"-stamped box is used only in these rifles:
.458 Winchester Magnum
.458 Lott

I don't recall what they use in the 500 Jeffery, but it would not surprise me if it is the ribbed box that is stamped "375 H-H."

CZ adjusts the feed rails, feed ramp, and maybe the follower (though I can't recall finding any differences in followers),
to do their feed jobs with a one-size-fits-all box.

Make sense?

I have also found that some of my re-barreled wildcat rifles that came with the ribbed box work better with the smooth-sided box.
Like the 500 Mbogo rebarreled from .416 Rigby.

quote:

Originally posted by 416Tanzan:
A second question can be added:

Can the CZ 458Win be rechambered into the 450 Rigby along with altering the same magazine? Or must a new magazine box and bottom metal be purchased?

(Bolt face, bolt stop, and rails need to be altered, too, of course.)

Bolt face and extractor, yes, rails and feed ramp yes, bolt stop no. They all have the same 3.8" length box and bolt throw.
The smooth-sided box of the .458 Win Mag or .458 Lott might work well depending on what is done to the rails and ramp, and it is roomier for the fatter case,
and should be better by the Mauser Co-sine Law.

Most big-bore rifles, even from the vaunted "legendary" custom builders and high-end, "bespoke" makers, are just make-do's with too-skinny boxes.
Parts is parts.

The smooth-sided .458WM box from CZ is about perfect, in internal width dimensions, for the 404 Jeffery,
but it is 0.2" longer than needed,
which is no problem.
But the way CZ does its feed jobs, the ribbed "375 H-H" box (slightly smaller width due to ribs being stamped into it from the outside) is easier to get feeding well, with less work.

Here are 2 of the "458 WM" boxes (also reinforced at front by Rusty McGee):

416Tanz, that's exactly where I was going to...

RIP, thanks for the clear info. This goes in the right direction: since I do not really like the 550's bolt shroud, nor the 550's safety, and more importantly do not like the idea of a 1-in 10" rifling twist on a 500gr bullet, I thought that the best way to get a 450 Rigby the way I'd like it to be is to start with an old Brno 602 in .458 WM, rechambered and worked on for feeding and bolt face fit.

Seems that the idea holds water...

quote:

Originally posted by Philip A.:
416Tanz, that's exactly where I was going to...

RIP, thanks for the clear info. This goes in the right direction: since I do not really like the 550's bolt shroud, nor the 550's safety, and more importantly do not like the idea of a 1-in 10" rifling twist on a 500gr bullet, I thought that the best way to get a 450 Rigby the way I'd like it to be is to start with an old Brno 602 in .458 WM, rechambered and worked on for feeding and bolt face fit.

Seems that the idea holds water...

A couple comments on the 1 in 10" twist.

First, 458 Win's usually have a slower twist and it would work fine for a 450 Rigby.

Secondly, with monometal flatnosed solids a faster twist is often better because the bullets are longer. I'm doing a 500 AccR Nyati at the moment in 12". Extra stability doesn't hurt a dangerous game rifle, it only affects flight in the 500-1500 meter range. That is far beyond my hunting experience. In Africa I've never "needed" a shot beyond 400 yards.

Phillip,

Yep, a BRNO 602 ZKK in .458 WinMag is all the parts you need to build a 450 Rigby. Try it with the original magazine box. It is a simple re-chamber, bolt face/extractor, and feed job.

Ditto 416Tanzan.
I have not heard of any BRNO or CZ .458-caliber factory rifle with anything other than a 1:14" twist.
That is the standard for Winchester, Ruger, Remington, etc.
Only a real riflecrank would consider anything faster, but 1:12" would be cool. Why not 1:10"?

Ed Lapour makes a great replacement safety and shroud for the CZ, I think my BRNO was a Wisner safety that is very similar.
With CZ you can get a Timney trigger, but with the BRNO you are stuck with the choice of two triggers from the factory. I like the curved, non-set option.
Here is my BRNO that has a Wisner safety and the original factory non-set trigger:

quote:

Originally posted by 416Tanzan:

quote:

Originally posted by Philip A.:
416Tanz, that's exactly where I was going to...

RIP, thanks for the clear info. This goes in the right direction: since I do not really like the 550's bolt shroud, nor the 550's safety, and more importantly do not like the idea of a 1-in 10" rifling twist on a 500gr bullet, I thought that the best way to get a 450 Rigby the way I'd like it to be is to start with an old Brno 602 in .458 WM, rechambered and worked on for feeding and bolt face fit.

Seems that the idea holds water...

A couple comments on the 1 in 10" twist.

First, 458 Win's usually have a slower twist and it would work fine for a 450 Rigby.

Secondly, with monometal flatnosed solids a faster twist is often better because the bullets are longer. I'm doing a 500 AccR Nyati at the moment in 12". Extra stability doesn't hurt a dangerous game rifle, it only affects flight in the 500-1500 meter range. That is far beyond my hunting experience. In Africa I've never "needed" a shot beyond 400 yards.

Don't forget - faster twist barrels will stabilize heavy bullets at lower speeds that would be unstable with slower twist rates... Plus they will not affect accuracy at hunting ranges or beyond - primary reason I'm using 9" twist rate barrels in my .423 and .500 caliber rifles...