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NitroXAdministrator
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.458 Winchester Magnum
      #391917 - 10/06/25 01:57 AM

https://africanxmag.com/2025/06/07/458-winchester-magnum/

.458 Winchester Magnum

https://africanxmag.com/wp-content/uploads/2025/04/458-1200x779.jpg

June 7, 2025Updated:June 7, 2025
Cape Buffalo

HISTORY
The .458 Winchester Magnum was a direct descendant of the .450 Nitro Express 3 1⁄4 inch and the .450 Watts. (Figure 1). The .450 Watts case was shortened from 2.850 inches to 2.500 inches and introduced in 1956 as the .458 Winchester Magnum.


Figure 1: The .458 Winchester Magnum cartridge (right) and its precursors.
It was designed for use against heavy, thick-skinned, dangerous African game species such as elephant, hippo, rhinoceros, and Cape buffalo (Figure 2).

Figure 2: The .458 Winchester Magnum – more than capable of stopping and dropping Africa’s biggest and most dangerous.
The exceptional sectional density of the 500-grain bullet, combined with a muzzle velocity of between 1,950–2,250 ft/s, provided the cartridge adequate penetration on these big animals. Rifles produced for this cartridge usually weighed under 11 lbs. The combination of these factors helped the .458 Winchester Magnum, in its heyday, to become the most popular dangerous game cartridge on the African continent.

Continued on link:
https://africanxmag.com/2025/06/07/458-winchester-magnum/

--------------------
John aka NitroX

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85lc
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Re: .458 Winchester Magnum [Re: NitroX]
      #391923 - 10/06/25 02:43 AM

John,

Thanks for posting. I had forgotten about the 458 Watt.

What is interesting (to me) is that after the 458 Win was developed, Jack Lott decided to lengthen the cartridge to 2.8" to get more power. That lengthered 458 Win became the 458 Lott which is essentially the 458 Watt.

--------------------
RB

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bwanabobftw
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Re: .458 Winchester Magnum [Re: 85lc]
      #391927 - 10/06/25 06:48 AM

Great article !!!!!!!!!!

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Claydog
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Re: .458 Winchester Magnum [Re: bwanabobftw]
      #391933 - 10/06/25 08:04 AM

The 458 win mag is super unappreciated. Had a cheap Zastava I used as a loan rifle and sometimes used a rusty old model 70 for backup and they performed as well as anything else did. Both open sighted and using federal factory ammo thought it hit noticeably harder than the 375s did. Would nearly say I am a fan of the 458 win mag.

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DarylS
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Re: .458 Winchester Magnum [Re: Claydog]
      #391934 - 10/06/25 09:23 AM

I've never had a .458 Win. Mag. but did have a couple. 458 2" "Americans," as well as a wildcat I sort of made up using a de-rimmed. 450 Alaskan case with a related rim to .532" to fit a standard magnum bolt face. I cut the new extractor groove at the same time.
This case, in a Model 70 (unfortunately post 64), had a capacity 7gr. greater than the .458 Winney Mangulum. It easily made 2,200fps with 500gr. Hornady's. I did not enjoy shooting those so I loaded it to the 2,150fps. with the 400gr. Barnes Spitzers(old style) I did enjoy shooting. The trouble was it took almost 10gr. MORE powder than the .458 2" to get that vel. So, I cut her back, rethreaded and chambered it for my .458 2" with the 3/8"leade. That allowed a normal seating depth as if the case was 2.2" in length. It easily did the 2,150fps with the 400's, 2,296fps with 360 Horn RNs and 2,059fps with the 500gr. Hornady RNS. I didn't shoot many of those, preferring the lighter bullets.

Incidentally, the difference between the Lott and Watts chambers happened on purpose and was at the end of the chamber's mouth.
Bench rest shooters call it the mean little shoulder. That is the 90 degree angle at the end of the chamber where the end of the case is supposed to just clear by .005" or so. It is then cut 45 degrees up to bullet diameter for the leade, but that mean little shoulder still exists.
What that shoulder did in the Watts chamber when fired with .458 Win Mag ammo, is strip off guilding metal from the side of the jacketed bullet when it road over that, into the throat(leade). This would prevent later chambering full length Watts ammo until the guilding metal was removed. This usually required a chambering reamer.
The "original" Lott chamber has a 3 degree angle from the case mouth of the chamber to the leade/throat. The bullet easily road up that slope into the leade and prevented the stripping of jacket material, if the shorter ammo was chambered and fired. This info from Jack himself, in one of the gun magazines when explaining why his chamber over the original Watts chamber. Small changes can make a difference.

--------------------
Daryl


"a gun without hammers is like a Spaniel without ears" King George V

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Rule303
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Re: .458 Winchester Magnum [Re: DarylS]
      #391938 - 10/06/25 11:21 AM

John, thanks for posting. The article was very interesting to me and Daryl's Post as well. All very informative to a person who has never delved into the 458Win.

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85lc
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Re: .458 Winchester Magnum [Re: Rule303]
      #391953 - 11/06/25 05:41 AM

Daryl,

Thanks for the descreption of the diference between the Watt & Lott. That makes great sense. I was wondwring why Jack developed the Lott, it seemed like "reinventing the wheel" but it is really an improvement. I knew that the Lott would also shoot 458 Win and 458 Lotts interchangable; I didn't know that the Watt would not.

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RB

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DarylS
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Re: .458 Winchester Magnum [Re: 85lc]
      #391962 - 11/06/25 10:58 PM

It was repeatedly said you could shoot .458 Win. Mag. from the Watts. What wasn't told was the guilding material fouling in the chamber. 1 or two shots might not make any difference, but quite likely 10 or 20 certainly would.
Jack fixed that with his change to the chamber design.
The same thing would happen in a .45/90 M86 (or any other (.45/90) if .45/70's were shot in the chamber. It was slightly more likely, the greater the difference in chamber lengths, such as shooting a .45/70 or .45/90 in a 3 1/4" chamber.
I'm surprised Phil Shoemaker hasn't addressed this thread. He used a .458 M70 for many years as a backup for his grizzly/brown bear hunts. IIRC he liked the 400 grain Barnes X bullet for that purpose at about 2,300fps.


--------------------
Daryl


"a gun without hammers is like a Spaniel without ears" King George V

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85lc
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Re: .458 Winchester Magnum [Re: DarylS]
      #391964 - 12/06/25 01:33 AM

I have a nice double rifle in 9.3x82. Several people recommended shooting 9.3x72r ammo in this rifle. I do not for the reason that you mention as the difference in case length is 0.4" and I am concerned that the chamber would be fouled. It isn't worth the hassle; I will get and load 9.3x82R brass.

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RB

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DarylS
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Re: .458 Winchester Magnum [Re: 85lc]
      #391968 - 12/06/25 04:58 AM

I would do as well. When I first read your post, I thought I read 6.3x62 - LOL. When you stated what several people had said, I thought WTF? Went back and saw my error.
Depending on the 9.3x74 ammo, could lose some case material into your chamber and bore as well. Much would depend on the ammo used. I have seen brass that became brittle, to lose chunks when fired.

--------------------
Daryl


"a gun without hammers is like a Spaniel without ears" King George V

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85lc
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Re: .458 Winchester Magnum [Re: DarylS]
      #391970 - 12/06/25 07:30 AM

Age brittle brass: I had 19 cased for a 9.3x82R that were set uo for a D chamber which is slightly smaller than the E or later unified chamber. The chamber of my rifle is based upon the unified 9.3x82r. Apparently the cases ,ay have been brittle.

I decided to fireform these to my double rifle. Many split which was disappointing (& costly). I had anealed the brass some 5 - 10 years ago when I was shooting a kipplauf in 9.3x82r that had a tight chamber, Of course, I now wish I had anealed that brass again before fire forming.

BTW, I used the same charge I used in forming some 450 3 1/4" from 450/400 3 1/4". The procedure I used was 10 gr bullseye and a case of cheam of wheat with a wax plug. The report was very mild and I didn't think there was an issue until I returned home and cleaned the brass. Cracks about an inch from the rim. Looking back, I could have used a lighter charge. The case is a very long (3 1/4"), narrow case andf perhaps the cerial bunched up, and combined with the amount expansion and somewhat brittle case, I got splits.

--------------------
RB

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DarylS
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Re: .458 Winchester Magnum [Re: 85lc]
      #391975 - 12/06/25 09:26 AM

I do think your situation was with brittle brass, however,

not entirely sure what causes splits. When we are forming .17AH from (even new) .22 Hornet brass, the normal 'deal' is to neck .22 Hornet down in the .17 AH seating die to .204" then use the FL die to neck to hold the .172" bullet.
Now, if the fireforming load is too light as when using 3 gr. bullseye with kapok, the shoulder will only partially form and will have splits around it's perifery.
A full power load, as used in formed brass, forms the brass perfectly, with no splits - ever.

--------------------
Daryl


"a gun without hammers is like a Spaniel without ears" King George V

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