CZ550 MAGNUM, 458WM Situation

[Ridge Runner]

First time in all my many years handling firearms and reloading that I have come across this bewilderment.

I have already called, left a message, and emailed CZ-USA regarding a possible barrel caliber marking/stamping error.

As the title says I have a situation; My CZ550 MAGNUM, is stamped 458WM.

I started to reload some 458WM ammo. Rather than the normal load and COAL I use for my Mark X, I decided to check the max COAL for the magazine and then chamber the round for max chamber length.

Looking over the max chamber COAL and mag measurements; they match the measurements for the 458 Lott.

My questions are:

Even though the rifle is stamped 458WM could or is it really a mis stamp and should be a 458 Lott?

As you can see in the photo below I can "short seat" the longer 458 diameter, 500 grain bullets out to 458 Lott, 3.585 COAL, by only seating the bullet ~3/8 to ~1/4 of an inch deep into the case.

Has anyone else had this experience?e
How did you reload your ammo for the capable larger case and chamber?

 

[CBeck]

Good read and may help…if I’m reading him correctly, CZ didn’t use a SAAMI chamber spec.

.458 Lott vs .458 Winchester – Lovin' The Big Bang

Posts about .458 Lott vs .458 Winchester written by bigborefan

bigborefan.wordpress.com

 

[Jack Stevens]

First time in all my many years handling firearms and reloading that I have come across this bewilderment.

I have already called, left a message, and emailed CZ-USA regarding a possible barrel caliber marking/stamping error.

As the title says I have a situation; My CZ550 MAGNUM, is stamped 458WM.

I started to reload some 458WM ammo. Rather than the normal load and COAL I use for my Mark X, I decided to check the max COAL for the magazine and then chamber the round for max chamber length.

Looking over the max chamber COAL and mag measurements; they match the measurements for the 458 Lott.

My questions are:

Even though the rifle is stamped 458WM could or is it really a mis stamp and should be a 458 Lott?

As you can see in the photo below I can "short seat" the longer 458 diameter, 500 grain bullets out to 458 Lott, 3.585 COAL, by only seating the bullet ~3/8 to ~1/4 of an inch deep into the case.

Has anyone else had this experience?e
How did you reload your ammo for the capable larger case and chamber?

Did you buy this 550 new or used? If used, couldn’t the previous owner have attempted to have the chamber converted to 458 Lott?

 

[BeeMaa]

Why not ream it out to (SAAMI specs) 458LOTT and restamp the barrel?

 

[Mark A Ouellette]

The .458 Win has a very long throat. In some rifles, one can seat bullets to Overall Length (OAL) equal or longer than the .458 Lott. The length of the rifle's magazine is the limiting factor.

The CZ550 Safari Magnum is rather easily converted from .458 Win to .458 Lott.

The article that @CBeck cited explains this .458 OAL.

Good read and may help…if I’m reading him correctly, CZ didn’t use a SAAMI chamber spec.

.458 Lott vs .458 Winchester – Lovin' The Big Bang

Posts about .458 Lott vs .458 Winchester written by bigborefan

bigborefan.wordpress.com

 

[roklok]

Not surprising to me, the .458 WM throat is long, enabling seating bullets way out if you have the magazine length to utilize it.

 

[Mark A Ouellette]

Below are SAAMI specifications for:
.458 Lott
.458 Winchester

These are the SAAMI specifications for the .458 LOTT

These are the SAAMI specifications for the .458 Winchester

Chances are the CZ550 Safari Magnums were chambered to CIP specifications.
"Permanent International Commission(the C.I.P.) for the Proof of Small Arms"
CIP specs MAY be slightly different than SAAMI specs.

 

[baxterb]

Have you taken the action out of the stock? When I sold guns long ago we had a few CZ 458 Lotts some through on special order that were not marked 458 Lott anywhere on the box but were stamped 458 Lott UNDER the wood line. All you could see was 458 win mag on the barrel, but if you took the stock off there was another line of stamping. We almost sent them back until a guy at CZ said to check. Maybe bad QC, but it did happen.

 

[DrBob]

Below are SAAMI specifications for:
.458 Lott
.458 Winchester

These are the SAAMI specifications for the .458 LOTT


View attachment 670772


These are the SAAMI specifications for the .458 Winchester

View attachment 670774


Chances are the CZ550 Safari Magnums were chambered to CIP specifications.
"Permanent International Commission(the C.I.P.) for the Proof of Small Arms"
CIP specs MAY be slightly different than SAAMI specs.

The simple acid test.... will a Lott CASE safely chamber? Plenty of people load the 458 to Lott length with Lott ballistics. I did it in a ZA Magnum Magazine article years back. My CZ 550 in 458 will not chamber a Lott case.

 

[Nhoro]

I think all of the above posters are right, the long Win mag throat allows an almost Lott length to chamber.@badboymelvin can give you some COAL for longer win mag loads. Maybe drop him a PM.

 

[BourbonTrail]

@Riflecrank is probably another good reference for this question.

 

[Hunter4752001]

By rights, a 458 Lott round shouldn't chamber in a 458WM chamber. Its not the oal but rather where the case mouth hits the start of the freebore/throat. All the suggestions re the rifle possibly having a Lott chamber may be correct. However, for safety sake have a chamber cast made and measured. The you will know exactly what you have a can make decisions accordingly.
ps. A Brno 602 or CZ550 in 458WM can easily be rechambered to Lott if thats what you want. Mine was.

For reference: the CIP standard can be downloaded from https://bobp.cip-bobp.org/en/tdcc_public?page=1&cartridge_type_id=3

 

[Safari Dave]

I bought a CZ 550 from a guy in what was advertised as a being in .458 Lott. The rifle was in such good shape and at such a good price, that I just paid him and took the rifle home to discover it was marked .458 Winchester Magnum. (I let him know, but didn't make a big deal out of it, because I would have bought the rifle anyway)

I had read (on this forum) that some CZ 550's marked .458 Win Mag would chamber .458 Lott, so I bought a box of .458 Lott just to see if they would chamber.

They would not.


Now, I can't decide to have the rifle rechambered, or sell a box of 19 rounds of .458 Lott.
(I have to keep one as a souvenir)


The bullets for .458 Win Mag are so good now, that I really doesn't think it matters to the animal.

 

[JG26Irish_2]

Goos chance it is just the long freebore of the 458WM chamber. But, the CZ can readily be re-chambered to 458 Lott also. If so, it should have had the new chamber stamped on it but... Maybe not.

 

[Ridge Runner]

Did you buy this 550 new or used? If used, couldn’t the previous owner have attempted to have the chamber converted to 458 Lott?

I bought it new. To replace my Mark X 458WM that is with the gunsmith and won't be ready in time for my trip to RSA.

Having ready some of the threads on here. It seemed liked CZ created the 550 MAGNUM as a factory base for those that purchase a CZ550 just to use as a custom build.

First range trip with new rifle: work out the kinks, loosen the stiffness, check the accuracy, clean the burrs off, etc. The 458WM ammo was short for the long magnum magazine and sloppy on chambering. The accuracy using the iron sights was good.

Fast forward to my OP.

 

[Ridge Runner]

Have you taken the action out of the stock? When I sold guns long ago we had a few CZ 458 Lotts some through on special order that were not marked 458 Lott anywhere on the box but were stamped 458 Lott UNDER the wood line. All you could see was 458 win mag on the barrel, but if you took the stock off there was another line of stamping. We almost sent them back until a guy at CZ said to check. Maybe bad QC, but it did happen.

No, I haven't separated the stock and metal. I will and respond back to you and via email to CZ-USA rep that I am in contact with.

 

[Ridge Runner]

As for CZ-USA. I sent an email directed to the Tech Department I had a response back early that same evening, instead of the next day or two.

 

[Safari Dave]

"Buggered-up" screwheads usually equal "No-Go" for me on buying used rifles...

 

[Ridge Runner]

I bought a CZ 550 from a guy in what was advertised as a being in .458 Lott. The rifle was in such good shape and at such a good price, that I just paid him and took the rifle home to discover it was marked .458 Winchester Magnum. (I let him know, but didn't make a big deal out of it, because I would have bought the rifle anyway)

I had read (on this forum) that some CZ 550's marked .458 Win Mag would chamber .458 Lott, so I bought a box of .458 Lott just to see if they would chamber.

They would not.


Now, I can't decide to have the rifle rechambered, or sell a box of 19 rounds of .458 Lott.
(I have to keep one as a souvenir)


The bullets for .458 Win Mag are so good now, that I really doesn't think it matters to the animal.

Curious:

What brand and bullet of 458WM ammo do you have?

 

[Safari Dave]

I have several different combinations of .458WM, because I've had a Winchester M70 for a long time.

I bought a box of Hornady .458 Lott in 500g FMJ/RN to try in the CZ.