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

Man, we travel the same way..

You might get me, but not for a lack of me trying! Ha!

Does anyone know what the mag length is on an Interarms Mark X? Any thoughts on these guns in general? How about compared to the Remington 798?

Sir Jerry,
VIP for sure then.

Sir Roo,
The Whitworth Mk X from Interarms of Alexandria, VA that I have, when still in .458 WinMag from factory (two of them)
were not opened up, had standard 3.4" mag box length.
I had one with rings in the chamber and had to re-chamber to .458/.416 Ruger.
It still has the original box which is too skinny to get 3 down in .458/.416 Ruger but handled .458 WinMag 3+1.
I still have not windowed that box or replaced it, will put calipers to it or see if I ever measured and wrote it.
Old Fugly you know about, had gunsmith open it to the front for .458 Lott when I was young and stupid.
I don't know if the Remington 798 had an H&H box length for .458 WinMag.
The Mk X when opened up to H&H length at the factory had it all done to the front,
unlike the Pre-'64 M70 that was opened mostly to the rear, for .300 & .375 H&H.

New .458 WinMag ammo images from MIB, many thanks to Sir Michael:





Load data for the pictured ammo is in the load tables above.

Comments to Sir Michael at MIB:

Michael458,
Plumb prolific of you.
Nice additions to the spread sheet for the 20″-barrel data for 2022.
It’s all good, the more powders the merrier.
Thank you very much.

What powder do I like best with the 404-gr Shock Hammer ?
AA-2230 of course.
I am going to take your loads with the old AA-2230 with a grain of saltpeter, however.

Why did Western Powders have to reformulate the AA-2230 and AA-2460 in 2016 anyway ?
Must have been a problem with the old formulae.
The change was said to have made them more stable in the thermoballistic way, less temperature sensitive.
That got my attention.

I never used any AA-2230 until 2017 when I had my .458 WinMag resurrection.
AA-2230 was the most commonly recommended powder by many when I resumed reloading for the .458 WM,
and I have not been disappointed.

I think AA-2230 and AA-2460 are the same chemical composition, my SWAG:
The tiny balls of AA-2230 are about a 50:50 mixture of perfect spheres and flattened ones (oblate spheroids).
All of the AA-2460 balls seem to be perfect spheres.
The mixture of flattened granules and spherical ones allows the AA-2230 a more compact loading for same weight of powder,
and there is a greater surface area on the flattened granules for quicker ignition.
So AA-2230 is a slightly faster powder requiring no compression when same weight of AA-2460 requires some compression.
Not much difference between them.
Flatten half the granules in AA-2460 and you have AA-2230.
I prefer AA-2460 for 450-500-grainers,
and AA-2230 for 400-grainers.

404-gr Shock Hammer
WW-Super brass 2.500″ trim
F215
3.480″ COL (crimped on third of five grooves)
39*F
25″ Shilen barrel, .458 WinMag:
AA-2230 81.0 grains >>> 2507 fps (5-yard), 2517 fps MV (estimated 20″ velocity = 2427 fps MV)

404-gr Shock Hammer
NORMA brass 2.500″ trim
F215
3.480″ COL (crimped on third of five grooves)
40*F
25″ Shilen barrel, .458 WinMag:
AA-2230 84.0 grains >>> 2535 fps (5-yard), 2545 fps MV (estimated 20″ velocity = 2455 fps MV)

Here are faster-burner powders that might get pressures higher but seem trouble-free in same rifle as used above:

404-gr Shock Hammer
WW-Super brass 2.500″ trim
F215
3.480″ COL (crimped on third of five grooves)
86*F
25″ Shilen barrel, .458 WinMag:
H4198 72.0 grains >>> 2504 fps (5-yard), 2514 fps MV (estimated 20″ velocity = 2424 fps MV)

404-gr Shock Hammer
WW-Super brass 2.500″ trim
F215
3.480″ COL (crimped on third of five grooves)
86*F
25″ Shilen barrel, .458 WinMag:
H322 78.0 grains >>> 2500 fps (5-yard), 2510 fps MV (estimated 20″ velocity = 2420 fps MV)

SHORTER COL FOR HIGHER MV:

NORMA brass
80.0 grains AA-2230 with 404-gr Shock Hammer, 40*F, 25″ Shilen barrel
3.380″ COL >>> 2488 fps MV
3.480″ COL >>> 2425 fps MV … lost 63 fps by loading 0.100″ longer COL

MORE POWDER MAKES UP FOR LONGER COL MV LOSS:

Same day, same rifle, same 40*F temp, same 3.480″ load with 4 grains more powder
84.0 grains AA-2230 >>> 2545 fps MV … gained 120 fps MV
(82.0 grains in 3.480″ COL is about equal to 80.0 grains in 3.380″ COL)

It is about a 10-hour drive to haul new-version AA-2230 to the MIB laboratory.
I am thinking about it. Owe you for that steak dinner at DSC 2013.

LOL, yep Big B, we can all get got, but damn sure wont get got rolled over on our backs pissing on our bellies like a bitch beagle dog.

More good stuff Sir Ron, Thanks for the technical leg work.

Sir Ron, Thank you, I forgot that you had done some work with the Interarms yourself. I've heard that opening up the action from the front is not a good way to go. No idea if that is the case with the Mark X or if it is just standard length. Are you happy with the guns themselves? Better or worse than an M70 or anything else you like?

I am a pretty basic reloader, and though I used to load long-range ammo for a few different calibers, I currently only load hunting ammo for my 45LC revolvers. Why do you prefer 2230 for the lighter bullets and 2460 for the heavier bullets? I would have assumed 2230 across the board, or if anything, 2230 for the heavier and 2460 for the lighter bullets.

I picked up a box of 325 grain Hornady FTX to play with. I have not picked a powder for them yet.
I can't take the recoil I used to but I won't need it for 100yd or closer shots.
My M77 Mark II also has a Shilen barrel on it. It was on it when I picked it up.

My 458 Lott barrel arrived for my Blaser R8 the other day and I took it out this morning for a test run. Gun weighs 10.5# loaded and I shot Federal 400g TBBC as well as Federal 500g Swift A-Frames and one 500g Federal 458 Lott solid.

The 400g TBBC's were an absolute joy to shoot. I'll post a short video later if I can. I plan to do most of my shooting in the future with 400's. I would have shot a bunch of them today but I only have the one box so far.

The 500g A-Frames were less pleasant to shoot, but were just fine as well. I have about 120 of them to shoot up for brass.

The 458 Lott cartridge was a skosh more recoil than the WM, but really not a big deal. The R8 design handles recoil very well. I probably have 60 of these to make brass out of.

If I am lucky, a more traditional 458WM bolt gun should show up late next week and then I will compare the two side by side.

I'm not crazy about having the Lott chamber, but I probably won't be loading long ammo anyway, so hopefully it won't matter much. I am looking into have JES recut the chamber to improve the throat.

rodeojoe,

Is it going to be Sir Rodeo, Sir Cooke, or Sir What ?


I have one good load for that bullet, it was another one-and-done 5-shot test
over an Oehler 35P with a 100-yard target.
That bullet is pretty soft, usually loaded to no more than 2100 fps in a .45-70,
but you could start here and work down if it is too destructive of venison:

325-gr FTX
COL = 3.300" seated long (seated on factory cannelure, COL will be about 2.990")
H4198 71.0 grains, F215 primer, WW-Super brass (or Hornady or RP brass OK)
24-7/8" CZ barrel, 59*F
5-yard Oehler velocity, uncorrected to MV = 2550 fps

Starting with 55 grains of H4198 and 2.990" COL would probably be like a hot .45-70 Govt. load from the restrained .458 WinMag.
You can play with low powder charge and +/- foam wad filler as well as COL to find an accurate load at desired velocity, I bet.

Sir Roo,

Those Whitworth Mark X rifles have been great, except for that issue with rings in the chamber of one .458 WinMag.
Factory reamer chatter is blamed.

I still have a half dozen Mark Xs in the safe: .358 STA, .375 WBY, .416 Barnes Supreme, .450 Barnes Supreme all on the "lengthened actions/3.6" mag boxes,"
and the two that started as unopened-up actions with 3.4" boxes for .458 WinMag.
BTW, my unaltered Mark X factory box for the .458 WinMag measures 3.410" long inside the box, same as the SC/FN M70 Super Grade.

Great thing about those Mausers is the mag box integral to floor plate, and thicker front wall than the sheet metal M70.
Factory Winchester M70 vs commercial M98 ?
Both need some work done on them.
Either one would satisfy me, ditto the Ruger M77 Mark II or Hawkeye, for a bolt action .458 WinMag.
If you have unlimited gunsmithing dollars,
the true Controlled-Round-Feed and Controlled-Round-Extraction of the M98 (and CZ 550 Magnum, BTW)
give them an edge over the others that are CRF only without CRE.

I was perfectly happy with AA-2230 for 450-500-grainers,
then I tried AA-2460 and found it just as good with a grain or two more powder, and for about same speed it gives slightly lower pressure with the heavier bullets,
according to Western Powders maximum load data.
Compress the AA-2460 a bit and it acts like AA-2230.
I consider AA-2230 to be merely a pre-compressed form of AA-2460.
AA-2460 grains are all spherical, maybe why I have seen it listed as "AA-2460s" some places.
AA-2230 looks like AA-2460s with about half of the grains flattened into oblate spheroids, but I repeat myself, my SWAG.

Sir Roo,

Very interesting.
Did you chronograph any of the loads for posterity ?

Have you checked the throat length of your "CIP" .458 Lott ?
Surely your .458 Lott barrel is made to current CIP which matches SAAMI.
Wouldn't it be weird if BLASER was using an old CIP reamer which had same throat at the end of it as on the .458 WIN MAG ?

SAAMI and CIP homologations for the .458 WIN MAG have never differed,
except SAAMI only allows 60,000 psi MAP
while CIP allows a +62,000 psi MAP for the .458 WIN MAG.

Running a SAAMI .458 WinMag reamer into the chamber of a SAAMI/Current CIP .458 Lott is indeed a good fix,
with non-cutting belt on that reamer.
Then you will be able to safely fire all .458 WM+ loads in your .458 Lott.

Sir Ron,

I have not chrono'd those Federal loads, but I have more and can do so at some point. I have also not measured the throat but will get that done in the near future as well.

Until today, all of my 458WM experience was with a stock M70, and it was pretty nice. The R8 is a pretty amazing rifle though and I look forward to wringing it out more fully, and in comparison to a Mauser (soon) and an M70(who knows when).

Incidentally, the gun handles recoil so well, that the 12.75" LOP that is on it right now was no issue whatsoever. I had wanted it to be 13", but Blaser USA messed up a bit and took an extra .25" off. I'm still sorting though possible solutions to make it 13". I have a second Professional stock that is at Blaser now, hopefully coming home with a 13.25" LOP. We will see.

How fast are you guys shooting lead bullets and how hard are they?
I remember seeing Sir Ron's coated and gas-checked bullets back in the thread, but is anyone using bullets that are only coated and not gas checked?
I'm interested in shooting some 18 Brinnell powder coated bullets as fast as I can without getting any leading.

Does anyone have a commercial source to buy correctly hardened, PC and GC bullets? Thank you.

Sir Ron, lets go with Sir TNly Joe

I have H4198 powder under my reloading bench. Also picked up 1,000 of the F215 primers last year.
Thank you for a starting point with the FTXers.

I have had this R8 for many years now, but have only really started to appreciate it more recently. Just got my 458 Lott barrel in and am planning to really just shoot WM ammo through it, though the Lott ammo is barely more noticeable than the WM. The R8 design really handles recoil well. My gun weighs 10.5# loaded, so not a lightweight.

https://pistol-training.com/the-one-second-split/

With cast, fit is more important than bhn. .460-1 is probably best but some bores will handle .459 fine too. Mine does. 18 bhn is plenty hard.

I can definitely get 459's, but I think I can get a local guy to make them 460 for me as well. How fast can I push them without GC's?