Home Forums Hunting & Shooting Express Rifles and Big Bores Only The great 458 Winchester. Everyone should own one at least once

Cast Bullets in the .458 WinMag continues with the question,
just what length of a .461" diameter right cylinder can be fitted into a SAAMI .458 WinMag throat ?



A little less than 0.5" length.
Keep it down to about 0.4" and it is an easy fit.
For a SAAMI .458 Lott, the corresponding length in inch units is ZERO.

Using an Accurate Molds drawing "Inspired" by the Lyman 457121 PH proves to be
very good for modeling the PH cast in 1:20 alloy, PC painted and sized to 0.459":

Previous flirtation with 72.0 grains of AA-2460s and deeper seating
proved to be of too high velocity for the two "46-485" bullets from Accurate Molds.
They exceeded the 2200 fps maximum for Nitro Express Modus Operandi.
So next, the load is decreased to 70.0 grains, and seating depth is decreased to 0.355" for both.
Now they both have air space in their cases, identical LR/net fill of about 93%.
That is a 478-grainer at 3.340" COL, quite lovely,
and the 491-grainer at 3.480" COL, a wicked witch of a bullet.
This requires just a taper crimp and no roll crimp into the full diameter bullet,
right in the middle of bearing band.
Both are hard alloy, BHN25, Eastwood Ford Light Blue PC paint, and have gas checks.





One often sees a little "s" tacked onto the "AA-2460s" name, and not the "AA-2230."
I finally figured this must be code for AA-2460s having all spherical grains of the same stuff that is in AA-2230.
AA-2230 has about half of its grains squashed flat to make it pack into a smaller space and burn a little faster.
I am going to try to remember to type the little "s" henceforth: AA-2460s

You may need a fine FN 458 WM there LDM.

Damn cool history lesson about MAHOHBAH Sir Ron, my old FN Browning is plenty light enough to carry all day tracking buffalo, it needs to go on my next trip, thought i remembered getting 2300 fps with 500gr Partitions at 3.340 inch, hell of a load Sir, even the old load at 2166 fps ain't going to bounce off anything, have read, but never had any trouble with H335 being slightly compressed with long 500gr NPT's, that ammunition is too good and too damn accurate to pull ; ]

Ok I need help. I have a stainless Portugal M70 in 338WM. I want to rebarrel it to 458 21-22”. Any thoughts on contour? NECG sights.

Why not have JES Rebore the current barrel and shorten it

Hey, smallfry, based on your reply to my .4** thread from last year, I know that you've had 458 WM's before. Unlike you, I was a newbie so based on the suggestions of Sir Ron & Sir Bob, I opted for a 23" 1:14 McGowen #5 for my first attempt at a Ruger MkII rebarrel. It's in production right now & based on emails I exchanged with their manager yesterday, I have my fingers crossed that I'll have it in hand soon. So unfortunately I can't give any experience-based feedback at the moment. But this thread is a great resource for ideas & the #5 contour often comes up as suggestion that's not too light or too heavy.

I've been reading this thread a lot since it's basically an encyclopedia of all things 458 WM. I had noticed back in 2021, you had toyed with the idea of rebarreling this rifle before. It's nice to see someone else who mulls over ideas for a long time before actually making a decision . Sir Ron's advice back then is probably still a good option:


As someone who like quantifiable data & the ability to weigh lots of options, I've always thought this thread would be a great candidate for an indexed & bookmarked document of lots of random facts & observations. Below are a bunch of contour posts from this thread:

Freki #5: https://www.24hourcampfire.com/ubbt...hould-own-one-at-least-once#Post18830841

A similar question: https://www.24hourcampfire.com/ubbt...hould-own-one-at-least-once#Post18492888

Contour & NECG: https://www.24hourcampfire.com/ubbt...hould-own-one-at-least-once#Post18512826

22" #5: https://www.24hourcampfire.com/ubbt...hould-own-one-at-least-once#Post17244502

M70: https://www.24hourcampfire.com/ubbt...hould-own-one-at-least-once#Post17250312

M70 #5: https://www.24hourcampfire.com/ubbt...hould-own-one-at-least-once#Post16134345

Shilen 5-1/2: https://www.24hourcampfire.com/ubbt...hould-own-one-at-least-once#Post17465522

Marcella #4: https://www.24hourcampfire.com/ubbt...hould-own-one-at-least-once#Post17586197

An assortment: https://www.24hourcampfire.com/ubbt...hould-own-one-at-least-once#Post18655405

#6 Light Target: https://www.24hourcampfire.com/ubbt...hould-own-one-at-least-once#Post19138289

Montana #5: https://www.24hourcampfire.com/ubbt...hould-own-one-at-least-once#Post15723148

Shilen #5: https://www.24hourcampfire.com/ubbt...hould-own-one-at-least-once#Post16947315

.4** Calibers: https://www.24hourcampfire.com/ubbt...alibers-whats-your-favorite#Post18807315

Of course you could always forego all of that research and hit the easy button:


What is the diameter of the 338 barrel at the 21" mark? If you subtract .458 from that, how thick will the remaining walls be?

On a somewhat unrelated side note, a couple of days ago, a BassPro store up in South Dakota listed a LH Winchester M70 Classic Sporter in .338 WM for $599. It looked great & there was a mad scramble by the southpaws in the LH forum to grab it. I wasn't fast enough but another member was. My opinion was they forgot to put a "$1," in front of that price. I didn't need a .338WM. But anyone who puts up a LH M70 for $599, I'm going to buy it & figure out what to do with it later.

Thanks for the info. I’ve been behind on my gun projects and have been wanting to screw another 458 together. Basically I need a new stainless barrel (not going to rebore) some bottom metal, sights and a stock. I just wasn’t entirely sure on the contour. Lots of info here.
Smallfry

I got some catching up to do.
First a couple of good loads before showing a shocker.
No scope adjustments, same as last outing, just letting bullets fall where they may at 50 yards:








So a charge of 70.0 grains of AA-2460s is probably going to be ideal for
NEMO loads with 480-500-grain cast bullets at 2150-2200 fps from a 24" barrel.
Make them .461" in diameter and hardcast, for the SAAMI .458 WinMag.

70.0 grains of AA-2460s is about the midpoint of 66.6 to 74.0 grain range recommended for
500-gr Hornady RNSN, for which 74.0 grains yields 2192 fps and 52,864 psi,
3.305" COL , 24" barrel.

70.0 grains, might go down to 69.5 grains to fine tune with hardcast, heh-heh-heh.

I was shocked to see how this load progressed in increasing 3-shot "group" size.







The third 3-shot "group" at 50 yards:



The tenth shot is the last one on paper:



The last of that load was wasted into the dirt.
Cannot fully explain this, but it seems that with 0.459" diameter and soft alloy, +1400 fps is too much, in a .458 WinMag.

Smacked with BP in a .45-70 might make a big difference.

The faster you push a hard cast the harder it needs to be for top accuracy. I thought that the powered coat might allow you to get away with it but it did not. I believe that at least .460" diameter would also aid accuracy

After the above shocking exhibition I await the larger diameter "Lyman Inspired" AM 46-467L.
It might "hardcast" into a 450-ish-grainer sizable to .461" diameter, PC-painted (blue) and plain-based.
Then there is that strange 46-502D that might be closer to 480-ish-grainer sizable to .461" diameter, also PC-painted and plain-based.

Enaa baasee' to Sir Darryl for the indexing.

Sir Smallfry, get a No. 5 Sporter from McGowen or PAC-NOR, 1:14" twist.
I am planning to do the same to a Ruger Hawkeye.
Was thinking of finally daring to do a 20" but now
maybe 21" like Phil Shoemakers Ol'Ugly ?
I have a rifle stuck in the gunsmith pipeline,
may need to find another smith ...

Sir Jerry,
Hopefully all was peaceful in OK on the latest April 19.
The two-legged vipers probably steer clear of OK when they find out you are keeping the peace there.

Agree.
I use a .460" sizer on my PC-painted BHN25 and it comes out 0.461" to stay.
Those always seen to work well in the long throat, .458" or .459" groove,
and the 1:14" twist is not too fast.
My Ruger No. 1 has 0.459" groove and 1:14" twist.

Maybe 1:20" would be better for the ultimate accuracy with hardcast, but 1:14" ain't bad.
And a PC-painted plain base might be as good as a gas check.
I was just getting rid of my leftovers in that last NEMO trial.
Had 16 of the soft PH,
7 of the hardcast AM 46-485N,
10 of the hardcast AM 46-485Z.
All done with leftovers.

Ready to cast hard for the .458 WinMag smokeless loads.

Simple recipe seems to be 70.0 grains AA-2460s for any hardcast 480-500-grainer
Nitro Express Modus Operandi loads: 2150 to 2200 fps in a 24" barrel.

I might be able to grind the 491-grainer down to 480-grains by cutting a cannelure deep enough
into its long full bearing base, for crimping, using the CH4D CannTool on the as-cast before painting, sizing and gas-checking.



Weigh the bullet after each crank and grind until it was reduced by 10 grains,
tedious and with lead exposure from biting my fingernails between weighings ... heh-heh-heh ...
Or just wait for the perfect 480-grainer to come along.

This one is pretty darn close to perfect for 480-grainer at 2150 to 2200 fps:



70.0 grains AA-2460s from the 24" Ruger No. 1 >>> 2185 fps MV according to Garmin XERO, at 56*F.
If not mentioned above, latest NEMO trial was at 56*F, yesterday.

It would be nice if the grease groove lined up for 3.340" COL instead of having the case mouth positioned in the middle of the drive band.
3.250" COL does line up nicely, with only a 0.090" greater free-travel of bullet to the rifling.
I must admit that with 3.340" COL and the occasional extra paint blob on that wide nose band's leading edge,
there is occasional resistance to chambering of the round in the Ruger No. 1, requiring a harder push on the lever to close the action.
Maybe a trial with 69.5 grains of AA-2460s and COL of 3.250" would work for NEMO.
478 grains is pretty durn close to 480 grains.
I think that passes for a 480-grainer amongst the Woodleigh HYDRO bullets, blah-blah-blah, heh-heh-heh ...
480 grains of .458-caliber bullet at 2150 to 2200 fps with smokeless sure is more fun to shoot than a 2-bore round ball with a couple of handfuls of BP.
And it was adequate for elephant.

Great to see the mission continues !
Hello to all the knights of the square table.
It seems we've lived through another winter.
No 458 news from me at this point. Still working on the house and homestead. Insulating the back 1/3rd of the house currently. That end of the house has been something of a Rube Goldberg experience to date. We did manage to have the coldest ambient temperature I've seen in The Interior this winter. -72° F that held for a full 12 hours. Preceded by days of 40, 50 and 60 below ambient. 40 below feels downright balmy compared to 70 below.
Now the geese, ducks, swans and cranes are coming back . On their way north.
Really enjoying this thread. Hopefully in the not too distant future I will have something constructive to add.

Sir Ron :
That AM46-485N load with 2460 looks to be just well suited for The Spruce King. That is the mold I will order. And see if I can find any Accurate 2460.
Looks like a real keeper of a load for the standard mag box length.

Thank you Sir Ron! I will go with a PAC Nor 1-14 stainless. Any thoughts or consideration on if they can chamber it correctly as well? How about bottom metal?
S.

Sir Spruce,
Enaa baasee' for the reply.
So you are living through some very interesting times, eh.
Confucius say "Man who builds his own house is never bored, just boarding whenever and wherever he wants."
How far are you from Fairbanks ?
I usually think of Fairbanks as the center of AK extremes.
What date was that -72*F ?
I'll try to avoid that date for my next vacation road trip in AK.

That AM 46-485N is nice, catalog comment at Accurate Molds say it was designed for .458 WinMag.
Order a two-cavity, 2.35" block, your choice of brass, aluminum or ferrous.
LEE 6-cavity mould handles fit, might have to do some fitting of the screw holes with variable RCBS mould handle holes.

Alloy I recommend is simple: Lawrence Brand Magnum Shot size 7-1/2, 10 pounds of it, plus a half-pound of 50:50 (tin:lead) solder.
Snip the solder into little pieces (an inch or two long) and mix well with the shot as you dribble them both into the melting pot.
That is BHN25 alloy aka 92:5:2:1 (Pb:Sb:Sn:As).
Water drop them and they are ready to go.
Hornady .45-cal gas check.
Eastwood Ford Light Blue powder coat paint is prettiest, IMHO.
Might soften from 25 to 21 BHN with the annealing caused by PC painting at 400*F for a half hour.
But they will age back to BHN 25 after 4 weeks and stay there.
Or use grease if you must, but make it bear grease heh-heh-heh.
Size with a .460" LEE or CH4D base-pusher bullet-sizing die, and they will be 0.461" after springback.

Sir Smallfry,
I have not had Pac-Nor chamber one for me, but I have heard only good from others who do that.
My Gunsmith is about to get me looking for another, so if you do it, let us know how it turns out and I might be next.

Bottom Metal might depend on specifics of old Classic versus newer FN/SC M70, and what kind of stock you have or do you want other possibles ?

Are you doing one of the Extreme Weather .338 WinMags from FN/SC, like this:



Whatever you do on an M70 it will probably have a sheet metal box needing some reinforcement on the front of it.
Here is one done when the Gunsmith pipeline was flowing more regularly, soldered-on stainless:



When the pipeline flow got sporadic I took matters into my own hands on a .458 WinMag M70 Classic.
That would be Marcella.
I found a piece of steel and used a hacksaw and a bastard file and J-B WELD:









J-Bubba WELD is as good as solder, in my bubba opinion.

Using the Pac-Nor barrel weight calculator,
I reckon that a 20"-barreled No. 5 contour is going to be only 2 ounces heavier than a 23"-barreled No. 4.
I will be doing a No. 5 sporter on my next one: