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I’m looking for an intermediate 0.458” cartridge between the 458 Win Mag and the 450 Rigby Rimless, based on the minimally altered 404 Jeffery case and a max COAL length of 3.6”.

Made up a dummy on a slightly shortened 404 J case but looks like the cartridge exists as a wildcat already. So I’m thinking about building a 460 G&A Short on a Winchester Model 70 Classic. I know that the parent case is the 404 Jeffery but I’ve searched for authoritative data on case length, cartridge overall length and ballistic performance (MV Range) but haven’t found it.

Other than an old G&A article by Tom Siatos describing the original 460 G&A in general terms, I haven’t turned up useful data.

Any leads on credible info on the data identified would be greatly appreciated to base a chamber reamer on.

Last edited by Wildcatter264; 07/03/22. Reason: Cartridge corrected to 450 G&A Short

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I have the poop on the .460 G&A from 1973, 1983, 1989 and 1994 pubs.
Includes the cartridge drawing and some handloading info.
Also have two reamer drawings, one from Clymer
and the other from Dave Manson with "GUNS & AMMO" specified as the customer for the reamer.
I'll get it up when I get done with some chores Wife has got me doing.
This stuff is right up my alley, since I am able to pontificate to no end on .458-caliber rifles, haha.


Ron aka "Rip" for Riflecrank Internationale Permanente
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Thanks, RC. That’s exactly what I’m looking for. I’ve had Dave Manson make wildcat reamers for me before and I’m planning on having him do this one for me as well. Cheers!


Is life so dear, or peace so sweet, as to be purchased at the price of chains and slavery? Forbid it Almighty God! I know not what course others may take, but as for me, give me liberty of give me death! P. Henry

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I reckon the .450 G&A Short Magnum (2.5" case) is simply a .460 G&A that is shortened in case body, below the shoulder, by 0.300".
Same neck and shoulder.
Could do it with same reamer inserted 0.3" shorter than the .460 G&A, using appropriate headspace gage.
Just make sure the .450 G&A Short Mag dies resize the brass to match the chamber.
However if you rechamber a .458 WinMag with a .450 G&A reamer, you might as well give it a .458 WinMag throat.
It is going to have one anyway unless you cut the barrel threads and set it back.
With a virgin barrel, you can have any throat you want.
I would want the .458 WinMag throat, then I could do practically anything with it that the short-throated .460 G&A could do.
Almost as good as the .458 WinMag loaded to 3.600" COL,
which can absolutely beat a SAAMI .458 Lott.

All I have is boiled down into the images below.
First from the 1983 BIG BORE book from G&A by Jack Lott:

[Linked Image]

[Linked Image]

[Linked Image]

The two .460 G&A reamers here are identical except the Manson reamer has a slightly shorter and narrower parallel-sided-free-bore,
and a more gradual leade: 0.459" diam., 0.150" long PSFB, 1.5-degree leade hemi-angle.
Clymer throat: 0.460" diam., 0.200" long PSFB, 2.5-degree leade hemi-angle.

[Linked Image]

[Linked Image]

[Linked Image]


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Since the Model 70 will handle the 375HH and 458Lott, seems like a full size 460G&A would also fit. Or maybe not if receiver is machined different at the factory and the OP is not starting with a H&H length bolt throw? If possible the longer case will allow for lower pressure to get the same performance as the short version or go a little faster if wanted.

Since the 450 Rigby was mentioned my understanding the claim to fame for that round was performance at low pressure. The hunters native to Africa seem to value that quite a lot. Or so I read from those who like the Rigby. I am just in this for the fun with a kind of big bore fetish.

I do remember reading about both back in the good old days when I had a G&A subscription. Today everybody loves the 458wm. Back in those days there were a lot of unhappy campers.

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The Model 70 Classic and later Winchesters M70s will make great 404 Jeffery rifles, I have one made from a .300 RUM re-barreled.
No doubt they would make a great .460 G&A or .450 G&A Short Magnum.
Either one will do fine.

After trying
.460 WBY X 2
.450 Dakota X 1
.458/.338 Lapua Magnum X 2
.450 Barnes Supreme X 1
.458 Lott X 2
.458/.416 Ruger X 1
.458 B&M X 1
.458 Winchester Magnum X A BAKER'S DOZEN ...

I choose the .458 WinMag, happily ever after.


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RC, exactly the info I needed.

My original intent was to rechamber a Ruger tang safety M-77 458 Win Mag to 450 G&A Short. However I’ve reconsidered and decided to rebarrel an infrequently used Win M-70 SG Classic 300 Win Mag to 458 Win Mag and rechamber to the full length 460 G&A. I’ll use the Manson reamer as I’ve used several of his reamers in the past. He’s easy to work with, fast and makes a great product.

I have experience, rifles and components in 404 Jeffery (P-64 Win 70) and 450 Rigby (Ruger RSM 416 Rigby rebored) so the project seems fairly straightforward. BTW the 404 J cases fit the unaltered bolt faces in both the Ruger 458 Win Mag and the win M-70 300 Win Mag. Removing the magazine block and altering the bolt stop in the 300 should allow the 3.6” bolt throw.

I’ve found that the 404 J with CEB BBW #13 400 grain solids at 2500 FPS MV shoots through an elephant broadside, so it’s a perfectly suitable rifle for African big game. However, a 458 caliber rifle on the 404 J case seems the best solution to this situation. Compared to my Ruger 450 Rigby the bolt throw will be a bit shorter/faster and the rifle handier (planned new 458 barrel will be 23” contour and brand TBD) and stock proportions more to my liking. I know only a rifle loony would appreciate these fine points, but there you go. It’s wildcat fever in full bloom.

Probably will sell the TS 458 Win Mag Ruger as I’m reluctant now to alter it. We’ll see the ultimate fate of the RSM 450 Rigby once the 460 G&A is completed.

Thanks again for the info, have work to do.


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FWIW, Good choice. I probably dont need to tell you this as I think you got 10x more experience than me on these projects. The industry makes pull through reamers. I did a garand with one becasue I could not access the chamber from the rear. It worked real slick. the bolt follows the reamer and when the bolt falls - done. Or, You can stop just a nit before the bolt is all way down to cut a min chamber. Not for DG, but; just saying there is that flexibility with the visual feedback.

If I had a Ruger RSM in 450, I would be thinking long and hard about letting that one go.

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fourbore,

Thanks for the info on the pull through reamer. I am not familiar with that technique. Any leads on manufacturers who would cut one in a wildcat reamer?

You’re right about the 450 RSM. That rifle is now just the right weight for the cartridge with a 500 grain bullet at 2350. The original stock was somewhat blocky for my taste so I had RJ Renner reconfigure it to his Rigby style. I like the way it handles now much better.

For the type of hunting I believe I have left to do large mediums and large bores are likely to see more use. So the RSM fits in that plan.


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I got that reamer from Manson.

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Thanks


Is life so dear, or peace so sweet, as to be purchased at the price of chains and slavery? Forbid it Almighty God! I know not what course others may take, but as for me, give me liberty of give me death! P. Henry

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It comes in 3 parts. The reamer, a long rod and a t handle. First time expense on the last two. I found a tap wrench worked fine as the T handle.

As an after thought, 460G&A might be asking a lot. Asking is free smile

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I called Loon Lake precision yesterday and found out they will make the 460 G&A to the original specs. I should receive it in the next 3-4 months.

Unfortunately I was told that due to the reamer dimensions they can’t make it as a pull through. I’ll need to get a set of headspace gauges next.

Planning to test a couple of magazine followers I have in the M-70 action I’m planning to use. Been looking at a few barrels in 458 Win Mag as a starting point to rechamber. I’ll need to see if I can get one without the cartridge stamp.

Next step is to run a 404 Basic case through a backed out 404 J full length die and expand the neck to 458 in the 450 Rigby die. Need to get an idea of seating depth with the 450 & 500 grain CEB BBW #13s to keep COAL at 3.6” max.

Starting to be an interesting project.


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Allow me to play devil's advocate.
You will have a bit of remnant .458 WinMag throat if you re-chamber a .458 WinMag barrel,
even with the .460 G&A reamer from Manson, unless you set the barrel back, and turn a 24" barrel into a shorter barrel.
Not a bad thing, either way.

The .300 RUM follower and windowed box that came in the factory M70 rifles should be the cat's meow for 3 down in the box.

Or try the Sunny Hill drop bottom metal for M70 .375 H&H and experiment with the followers and feed job.

I see the .460 G&A as a welcome way to re-barrel or rebore an unwanted .375/404 Jeffery or .410/404 Jeffery
to make a more interesting rifle.
The .458 is tops.


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RC,

After looking over the 460 G&A specs and drawings I’m having a hard time understanding how rechambering a standard 458 Win Mag barrel will leave part of the original throat. Please explain so I might better understand. 458 Win Mag case is 2.5” COAL is 3.34” both much shorter than 460 G&A specs.

As a matter of fact, it seems to make sense to start with a 458 Lott chambered barrel to rechamber to 460 G&A. Both cases are 2.8” long and COAL is 3.6”. What do you see as a problem with that plan?

BTW, I’m planning on a 23” barrel, probably a Douglas with a target weight of +/- 4 lbs. Target rifle weight is 10-10 1/2 lbs.


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I wouldn't go lighter than 10 1/2 pounds including scope if you plan on running a 500 grain projectile at 2300 fps or above. If you were using the .450 G & A Short running a 500 grain projectile at 2200 fps then I'd aim for no less than 10lbs including scope.

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Originally Posted by Wildcatter264
RC,

After looking over the 460 G&A specs and drawings I’m having a hard time understanding how rechambering a standard 458 Win Mag barrel will leave part of the original throat. Please explain so I might better understand. 458 Win Mag case is 2.5” COAL is 3.34” both much shorter than 460 G&A specs.

As a matter of fact, it seems to make sense to start with a 458 Lott chambered barrel to rechamber to 460 G&A. Both cases are 2.8” long and COAL is 3.6”. What do you see as a problem with that plan?

BTW, I’m planning on a 23” barrel, probably a Douglas with a target weight of +/- 4 lbs. Target rifle weight is 10-10 1/2 lbs.


The 458 Win mag has a much longer throat than does the 458 Lott



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Originally Posted by Riflehunter
I wouldn't go lighter than 10 1/2 pounds including scope if you plan on running a 500 grain projectile at 2300 fps or above. If you were using the .450 G & A Short running a 500 grain projectile at 2200 fps then I'd aim for no less than 10lbs including scope.

My current 450 Rigby Rimless is 10 lbs 10 oz, iron sights no scope. Controllable with 500 gn bullets at 2350-2425 fps for follow ups. I wouldn’t make it any lighter.

The 460 G&A I’m working on now should come in about 10 1/2 lbs - no less - planning a 500 gn bullet at about 2300 fps. The main variable to achieve that weight will be the barrel contour. Plan to call Douglas to get an accurate weight of one of their 23” barrels chambered in 458 Lott and adjust the countour based on that. A few ounces will be added by peep sight, barrel band front swivel, NECG Masterpiece Banded ramp FS. Haven’t decided yet whether to keep factory bottom metal with a different follower, spring, magazine box. That decision may add a few ounces as well.

I want to make sure that the rifle retains balance when mounted and aimed. That’s critical IME for first and follow up shots.


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Originally Posted by jwp475
Originally Posted by Wildcatter264
RC,

After looking over the 460 G&A specs and drawings I’m having a hard time understanding how rechambering a standard 458 Win Mag barrel will leave part of the original throat. Please explain so I might better understand. 458 Win Mag case is 2.5” COAL is 3.34” both much shorter than 460 G&A specs.

As a matter of fact, it seems to make sense to start with a 458 Lott chambered barrel to rechamber to 460 G&A. Both cases are 2.8” long and COAL is 3.6”. What do you see as a problem with that plan?

BTW, I’m planning on a 23” barrel, probably a Douglas with a target weight of +/- 4 lbs. Target rifle weight is 10-10 1/2 lbs.


The 458 Win mag has a much longer throat than does the 458 Lott


Yes, indeed.

Here is a Manson reamer for .458 Lott (SAAMI)
and a Clymer reamer for .458 Winchester Magnum (SAAMI), side by side:

[Linked Image]

[Linked Image]

Here is a drawing showing that the throat of a SAAMI .458 Lott lives entirely inside the throat of a SAAMI .458 WinMag:

[Linked Image]

The Manson 460 G&A throat is living a little bit more so inside the throat of the .458 WM.
Infact, you will have an itty-bitty length of the SAAMI .458 Lott throat left if you rechamber one to .460 G&A without setting the barrel back an itty-bitty bit.


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Some Winchester M70 rifles that could be re-worked into 460 G&A:

[Linked Image]

[Linked Image]

[Linked Image]

[Linked Image]

[Linked Image]

[Linked Image]

[Linked Image]


Ron aka "Rip" for Riflecrank Internationale Permanente
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.458 Winchester Magnum, Magnanimous in Victory
THE WALKING DEAD does so remind me of Democrap voters. Donkeypox.
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