CZ550 MAGNUM, 458WM Situation

[Ridge Runner]

Missed the Editing time.

Regarding my reloading development;

As I was testing/ working on COAL length,
I did notice with the longer COAL a lot of the previous sloppy 458WM cartridge chambering I noticed at the range vanished allowing a bit more smoother bolt action.

 

[Triathlete3]

I had to call CZ on mine to make sure it was factory done because as you can see from the picture the 458 Lott stamp is more crude and aftermarket than the 458wm. But, they assured me it left the factory that way. Is it possible this is one that slipped by QC? Yes. I would get CZ the serial number to check.

 

[Ridge Runner]

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.

I use the Hornady 500gr DGX AND DGS for reload development. I was hoping you might have picked up something other than 500 gr bullets, and in Nosler, Norma, Swift, or Barnes.

 

[Ridge Runner]

I had to call CZ on mine to make sure it was factory done because as you can see from the picture the 458 Lott stamp is more crude and aftermarket than the 458wm. But, they assured me it left the factory that way. Is it possible this is one that slipped by QC? Yes. I would get CZ the serial number to check.

 

[BeeMaa]

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.

If it were me (and it clearly is not), I’d have it reamed to 458LOTT, have the barrel stamped appropriately and open up the magazine to accept the longer cartridge if necessary.

Having the ability to shoot either 458WM or 458LOTT is the first bonus. The second is the ability to shoot higher SD bullets. You can always load the LOTT down to WM levels, but it doesn’t work the other way around.

A saying from the hot rod car world, “there’s no replacement for displacement “. Holds true in this case as well.

 

[Riflecrank]

The original .458 Lott wildcat was a SAAMI .458 WIN MAG that simply had the brass-accepting portion of the chamber lengthened so it blended into the existing remnant throat
"LONG, Wide-Based LEADE ONLY" of the .458 WIN MAG: 0*29'30" leade hemi-angle or 0*59' leade cone angle, just under a one-degree cone angle.
Maximum COaL (or "COL" not "COAL") possible in chambering a round was the same for both the
wildcat ".458 Lott Like Jack Built" and the SAAMI .458 WIN MAG.

SAAMI and CIP specifications for the .458 WIN MAG are identical in chambering,
they differ only in Pmax/MAP.
CIP allows Pmax of 4300 bar (~ 62,350 psi) for both .458 WIN MAG and .458 Lott.
SAAMI governs the .458 WIN MAG down to MAP of 60,000 psi
but allows the .458 Lott a MAP of 62,500 psi.

The initial CIP homologation of the .458 Lott was in 2000 AD (00-08-24 by their date format).
The throat was same as on the SAAMI & CIP .458 WIN MAG, which are identical, unchanged since 1955-1956 WRAC engineering origin.
Thus the original CIP .458 Lott could be loaded to 0.300" longer COL than the .458 WIN MAG
before bumping the bullet into the lands.

A revision in 2002 by CIP (02-05-15) for the .458 Lott showed the same throat.
Finally in 2006 (06-05-16) CIP changed the throat to match the SAAMI throat on the .458 Lott.
A-Square had been diddling the SAAMI specs on the .458 Lott since the mid 1990s and finally got it homologated about 1998 IIRC with the short and tight parallel-sided free-bore that I love to hate today.
Mastermind Art Alphin's A-Square was based in Kentucky then.
The SAAMI .458 Lott may be the result of too much Bourbon and/or moonshine.

Early CZ 550 Magnum .458 Lott rifles will have various forms of crude stampings of "Lott"
about the original factory roll marking for CAL. .458 W. M.
Those .458 WIN MAG barrels were re-chambered with the original extra-long throats from 2002 CIP reamer specs.

You could not find the ends of those throats even with a +3.8" magazine box.
You also could not achieve 2300 fps with 500-gr factory ammo due to all the pressure let-off of the throat. 2150 to 2200 fps was more like it, even with the 25" barrel.
Just a routine .458 WIN MAG with a mag box 0.4" shorter will do that, at 60,000 psi or less.

The only CZ 550 Magnum .458 Lott I owned was like that, even after they started offering them in the "Kevlar" or "Aramid" synthetic stocks. I traded it off.

I guess CZ-USA eventually started using the latest CIP .458 Lott reamers (same as SAAMI).

The CZ 550 Magnum .458 WIN MAGS have always been the same regarding throat.

Run the current CIP/SAAMI .458 Lott reamer into a CIP/SAAMI .458 WIN MAG chamber
and it will allow you to load your .458 Lott cartridges to as long a COL as possible in the CIP/SAAMI .458 WIN MAG.
Call it a ".458 Lott+"
just like the original .458 Lott THAT JACK BUILT
and you can now safely use the same handloads as we do in the ".458 WM+"
recently re-dubbed the .458 WIN MAGA.
Beats the CIP/SAAMI .458 Lott.
Either higher MV or lower pressure or both.
Physics does not lie.
THROAT THROAT THROAT.

 

[Riflecrank]

Ridge Runner,
Are you just now catching on to the fact that a SAAMI/CIP .458 WIN MAG
can be loaded to longer COL than a SAAMI/CIP .458 Lott ???

Any make of rifle in standard SAAMI/CIP .458 WIN MAG chambering can be single-loaded to beat the SAAMI/CIP .458 Lott, whatever the magazine length.
Single-shots are especially good for that, like my Ruger No. 1.
I also have a CZ 550 Magnum and I use the 500-gr TSX bullet at about 3.760" COL and get +2300 fps from either 24" or 25" barrel.

Next up for my testing is a TC Encore with 20" barrel:

 

[Riflecrank]

Whatever problem this web site was having with me seems to have resolved.
I can post again.

 

[BeeMaa]

Next up for my testing is a TC Encore with 20" barrel:

Could you please let me know the weight of the T/C Encore as shown? You may also want to place your ophthalmologist and dentist on speed dial before touching that thing off. Detached retinas and broken teeth are not fun.

 

[Riflecrank]

7 # 3.6 ounces as bare/empty rifle with just thread protector on the muzzle and TSOB rail on the barrel.
Add Slip-On pad and ammo carrier and suppressor: 8# 10 oz.

10 pounds is perfect comfort, easily exceeded with this rifle.
The suppressor adds some velocity to the 20" barrel and also reduces recoil a bit.
20" barrel becomes 27-5/8" to end of the old original Bushwhacker 46 from Griffin.
Overall length of rifle is like a bolt-action with 23-5/8" barrel.
Not bad.
Jim Shockey did the world with a TC Encore .50-cal. muzzleloader.
I think it is time for him to step up his game to .458 WIN MAG for the same slam.

 

[Milan]

... 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?

Can't answer that without seeing/testing the rifle. But if it is a .458 Lott, firing 458 WM will be OK. Also you should know that Brno 602/CZ 550 Safari rifles had a magazine that was too long for .458 WM but perfect for .458 Lott and that's why they were so easy to rechamber. As a matter of fact, if I got a .458WM, Id' make a Lott out of it anyway.

 

[Milan]

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.

Just re-chamber to .458 Lott and be happy.

 

[One Day...]

I am not sure that I understand what the problem is...

To see if you have a Lott chamber or a Win chamber: try to chamber a .458 Lott brass. If the bolt closes, it is a Lott chamber. If the bolt does not close, it is a Win chamber. Period.

In the name of Occam's razor principle of parsimony, I am prognosticating that you have a .458 Win with a long throat, Ridge Runner. Mistakes / wrong stamping are very, very, very (did I mentioned very) rare on factory rifles...

Alternatively, what may be more common, in this specific caliber's case, is John Doe bubbasmith pushing at home a reamer in the chamber and not restamping the barrel...

Cartridge OverAll Length (COAL) is nowhere near as meaningful - I was tempted to write "irrelevant" - as brass maximum dimensions when it comes to chamber dimensions. COAL is more relevant to action and magazine length and, of course, throat.

PS: Admittedly, with the Win and the Lott headspacing on the belt, it may not be as clear cut as 10 mm vs. .40 S&W, but the principle remains the same...

 

[Ridge Runner]

The rifle was bought as new, unfired. There are no markings to indicate this rifle was reamed to 458 Lott after market.

I tested 6 rounds of 458WM with a case overall length of 3.556 to 3.579. The 458 Lott case overall length for the Hornady 500 grain round nose is listed at 3.585. Compared to the 458WM using the same bullet case overall length is 3.310.

At 50 yards: The 458 Lott lengths were 3-1/2 inches high with a 1-1/2 inch group. The 458WM lengths were centered zeroed with a 1-1/2 inch group. The powder charge, and primers used was the same for both case overall lengths; 63.8 grains of Reloader 7.

This test was just to check out the minimal amount of bullet performance with only ~ 5/16 of an inch seated in the 458WM case.

The next range day will be ballistics testing of the longer length rounds.

The average velocity with the current 458WM loads is 2089 fps. Velocity range: 2069 to 2109.
Load Data:
Bullets: Hornady DGS and DGX, and Woodleigh 500 gain Solids
Powder: Reloader 7, 63.8 grains
Primer: CCI and Winchester Standard Large Rifle
Length: 3.310 to 3.289 inches

I will be ordering some 458 Lott brass to do more testing but that will be in June when I return from RSA.

Problem 1: and I will be contacting Shawn at CZ-USA to verify, that this rifle is capable and safe to use 458 Lott loads before shooting 458 Lott ammo in it.

Problem 2: The reason for wanting a 458WM is to have sort of double duty rifle: 458WM and 45-70. A choice of calibers/loads for a wider choice of animals.

The 458 Lott magazine and chamber lengths are too long for proper functioning of the short 45-70 cartridge.
________________________________________________

Here is the email I received from CZ-USA:

Good afternoon,

That model is indeed chambered in .458WM. I’ll include my gunsmiths response upon my inquiry about the rifle.

.458 Win Mag will fit and fire with no issues in a .458 Lott chamber, since the latter is essentially just a longer .458 Win Mag by exactly 0.3 inches.

The only real problem would come when you try to fire the longer Lott right after the Win Mag, which would turn the carbon buildup into diamonds against the chamber wall. (exactly like firing a .357 Mag right after shooting some .38 Special)

Seeing as how that rifle left our warehouse well over a decade ago, it is possible that someone could have reamed it deeper but neglected to re-stamp it, but who knows?

That rifle no longer has parts available since the last time we sold one of those models was in 2019, but both calibers were produced by the factory and both use the same magazine body, so him seeing either cartridge fit in there is a non-issue.


Shawn Stark
Customer Service Representative
CZ-USA | Dan Wesson
Main: 1-800-955-4486 | Alt: 1-913-321-1811