.300 WinMag to .458 WinMag Conversion

I have a real nice M70 .300 WinMag Super Grade that is destined for some kind of change. It has a real nice stock that many of you have seen in a prior post.
 
 ANYWAY ... this dang rifle is too heavy to lug around in the black timber while elk hunting, and I've decided to build a pair of matching WSM's, a .300 or .338 (haven't decided which yet) and .257 WSM, leaving me with a spare hot 30.
 
 I'm pretty new at the big bores, but find them fascinating. It seems to me from my reading that the .458 WinMag is about all I can get from this M70 action, but I've also read that tis caliber has trouble reaching the listed 2200 fps.
 
 Can anyone shed any light on this caliber for me? How much work am I looking at to convert the .300 Winny into a .458 Winny? Is this caliber redundant with my .375 H&H, or am I getting into a caliber that offers a significant step up in kaboom? What else to do with that .300 if not this?
 
 Rick

Rick, the 458 would fit just fine in the 300 action, just replace the barrel and you're on your way to bruised shoulders! [Linked Image]

Many posters on other boards have maligned the 458 for less than ideal performance, mostly on dangerous game. Velocities are usually not as advertised, is the usual complaint. I doubt you would get a complaint from an American elk or ground squirrel, though.
 An option you might explore is the 458 Lott. You could still fire the original 458Win in it, but for the really big squirrels and big stuff like Cape Buff (you ARE going to Africa soon, right?), the performance would be up to snuff- think 500 Grain sledgehammers at 2400 fps.
 Another option is the 416 remington, which is also very popular and doesn't suffer from the reputation of the 458, in performance or recoil. Both of these is a definite step up in performance from the .375, but I'll let you test them out first while I smile shooting my .375. [Linked Image]

- Sheister

A 416 Taylor would fit right in that action. 416 Rem. and Rigby velocities in a 2.5" case. 400 grain bullets at 2400 FPS. Just what the Dr. ordered.

Ahh Rick, your finally coming around...
 
 (Must of rained in LA, and now you can breathe again)
 
 [Linked Image]

Your .458/300WM sounds like a fun project. The 425 Express is an established wildcat which uses 300 Win Mag brass necked up to accept .423" bullets. I have load data for it here...
 
 http://www.geocities.com/bw_99835/page18.htm
 
 Also, there is a picture of a 300 Win Mag case with a 400gr .416" Hornady seated in to the proper C.O.L. for a M70 magazine. That will give you an idea of what the cartridge (.458/300WM) will look like, just smaller.
 
 Now, about that 416 Taylor? If we just knew somebody who had some info on it...
 
 [Linked Image]

You may want to go with the 416 Howell, John Ricks has the reamer for it. I should be getting mine pretty soon. It started life as a 30-06.

Rick
 
 I have some 400 X's that haven't been tried yet, but am very gratefull looks can't kill. At just a tad under 2400 fps., these should make up for any alledged shortcomings of the 458 with the 500 softpoints.
 
 Shooting 350sp or 300x's at just under 2600 fps. should handle any North American safaris. Recoil from these are just a big freindly shove, or similar to your 375.

Rick,
 
 Go with the 458, it is a very versitile round, can be loaded down to 45-70 levels, or up to most impressive levels! I won't get into the bad press issues, but I think of more importance is Winchester really messed up by not loading it for NA, launch a 350 gr @ 2500 fps, recoil is the same as a 375 H&H, and it hits with authority!
 
 Conversion is straight forward, just a barrel swap.

How about a 458X2inch. I believe it also is called the 458 Alaskan. I have no experience with the cartridge but do have one in my collection. It is merely a 458 Winchester Mag. reduced in length to 2 inches long.

Rick. I would also check into beefing up the stock. Factory .458's have steel bolts installed to forestall stock splits from recoil. E.

E:
 
 Well, you've seen the stock, so I will definitely keep that in mind.
 
 I still am not sure if that stock is going to work out. I sure hope so, as it would really be a nice piece if I could get it to work.
 
 Decisions, decisions.
 
 Rick

Rick,
 
 I was going to mention the stock issue, but got pulled away mid post and forgot.
 
 Here is a superb article on stocking a heavy rifle. http://www.swervingatom.com/accuratereloading/lott.html and keeping it from going to bits, or repairing it when it does.
 
 I highly recomend a second barrel mounted recoil lug on 40 caliber and up guns.

Well, I've had no trouble with velocities in mine. 400grn Federal Premium Trophy Bonded (mouthful, eh) trips the chrony at about 2450 fps. Haven't chronied the 500 grn solids yet. Rabid_on_the_Right has a set of 458 dies for me, so if we can just get together sometime I'll try some handloads. [Linked Image]

badger.

badger
 I'd be happy to mail them to you if you wanna wip some loads up to shoot in the poatal when littlebit gets done deer hunting [Linked Image]

I might have to break out the video camera for that!!!!!
 OOoohhhwee.....I think we should get out from under the tin roof first though...
 Mike

Well, I've been gone for far toooo long...
 Rick, you're throwing bad money after good to make such
 a conversion. The 458 can barely make 2100fps and that is
 really smoking. While on the other hand my 450 Ackley makes
 2350-2375 without breaking a sweat using the A-Square 465grs (but now I'd use the Woodleigh 480's).
 
 Also your 300 probably does not have TWO RECOIL LUGS, and this is mandatory for 458 and 450 Ackley/Lott/Watts...
 Not to mention the barrel channel will have to be hogged out excessively.
 
 My advise, is to mothball the .300 (cause I can never really sell anything), and start with a factory .458Win Mag. I did this, and had it converted into 450 Ackley and it works like a charm. You'd need to ream out the chamber, and replace the magazine box with the .375 length box, but that's about it. I shot a Cape Buffalo and Elephant with this combo, and the Buff dropped with 1 shot, and the Elephant took a couple more, but the solids penetrated LENGTHWISE from her hip to her chest...
 
 Drop me a line, and I'll send you a couple photo's...

Rick,
 
 What a dilema, to many rifles and barreled actions lying around. I think you will find that the time and money invested for such a project is not very cost effective. You can find several used Interarms Zastova M98 Mauser Mark Xs chambered in 458 Win Mag for around $450 and buy new Zastava M98 458 Mags for around $600. For the money your spending to convert the 300 WM (barrel and stock), you could buy a used 375 H&H, Mark X M98 Mauser, rip the barrel off and rebarrel to 458 Lott without restocking most likely (depending on your barrel contour).
 
 There are also real bargains on used 458 Win Mags in Model 70 Safari rifles all over the place, not to mention 375 H&Hs waiting to become a 458 Lott after rebarreling.
 
 If I were you, I would build both the 300WSM (180 grains bullets) and a 338WSM (225-250 grain bullets) and send the other 300 Win Mag action over to Rifles Inc for a new rechambering in 25 STW. For $325 you get a full conversion wearing a new 25 STW Shilen chambering and barrel. The 25 STW will smoke the 257WSM under the table with 115-120gr projectiles traveling at plus 3550 fps and ripping 80 grain bullets over the vaunted 4,000 fps mark. Nothing in the .257 class touches it.
 
 Just food for thought, nothing gospel here.
 
 Take Care,
 rossi

RickBin
 
 You didn't mention if the M70 is a push feed or claw extractor. In any case, pull out the box magazine, remove the spacer at the rear of the mag, get a 375 H&H length follower / spring, modify (or replace) the bolt stop (push feed), modify or replace the standing ejector and bolt stop (if claw extractor) and you have an action that will take any of the 3.60" length "belted magnum" cartridges.
 
 IF you do go with one of the heavy hitters, you should look into an extended recoil lug / bedding system and cross bolts or internal "lock bedding" of the stock.
 
 By the way, you can go to a REAL heavy hitter with that M70, by opening it up for the (416) Rigby style of case with an OAL of up to 3.95+". Yes, been there - done that, and got pictures of the results. In fact, I've got a modified (as mentioned above) action (M70 of course) sitting next to my monitor waiting for a "wild hair" idea, barrel, stock and scope.
 
 Good hunting,
 Dale (M70)

Just sell it!
 
 This is like buying a car with a 305 small block and asking how to switch engines to a 350.
 
 I did not read the other posts.

Don,
 
 I disagree a little bit. It's not like Rick is buying the rifle, just to rebarrel. He already owns the rifle, and wants to do something different with it.
 
 I would agree, that it's a shame to start cutting on that nice Super Grade stock.
 
 Perhaps it would be better (at least to me) to pick up a nice 1909 Argentine Mauser, and have it rebarrel and stocked. Of course, Rick would want a new trigger, side swinging safety, maybe bottom metal (but it is an 1909 Argentine), etc. [Linked Image]

$$$
 
 Here's that picture of a 300 Win Mag case necked up to .416. The cartridge on the left is a fireformed 416 Taylor. The right one is the 416/300WM, naturally "unfireformed" as I don't know of anyone with a rifle chambered for such a round. Try and imagine it with a more defined ("sharper"?) neck.
 
 [Linked Image]

Take care.

Rick, I SAW the picture and I DO wish that rifle were left handed so I could take it off your hands and save you from this awful dilemma.
 
 Jeff

Rick,
 
 Can't believe you'd waste all that money on a CRF.

(What happened to the wink?)
 
 Regardless, It's time you discussed your project ideas with Mr Ricks: [email protected] and http://home.earthlink.net/~rifles/
 
 Blaine

Since you're going to have to rebarrel and have some gunsmithing done why not make it a .404 Jeffrey. Much classier than a 458 win mag.

.404 is okay, but 450 Ackley or 458 Lott is so much more fun...
 
 My first hand experience of poking an Elephant from Stem to Stern proves there is enough penetration!! Talk about Viagra for hunters!!

Will the 416 Talor fit into a Ruger M77,3.4" box? I have one in 338 and may be getting another action. Gotta do something with it.
 PS: a 305 to 350 swap is a no-brainer,done it a few times.

Good thing you didn't handle it Jeff. You would be learning to shoot right handed if you had. E

Rick
 I have a 458 barrel here from Shilen setting on the shelf. Think about it.. I also have a 458 Lilja barrel in a # 9 contour that I am going to make a bench gun some day just to aggravate the bench shooters ! A friend of mine has a 45-70 I built that will shoot in the 3's and 4's with a pure lead swaged bullet in a paper patch. Sure is a lot of fun to see the look on there faces when they see those groups !
 Charlie Sisk

You should sell the Winchester and by a new/used big bore rifle in .458 win or .416 rem.
 
 I am sure that you will find someone who wants to take the winchester off of your hads for plenty of $$ to pay for your new rifle.
 
 You also will get a rifle designed from the bottom up for heavy recoil.

Charlie you have some sick...sick friends!!! I like It... [Linked Image]

Mike

Mr. Sisk:
 
 What kind of action is that accurate .45-70 built on?

Sir
 Mine is on a Siamese Mauser, Shilen barrel, laminated stock.
 Charlie Sisk

Mr; Sisk:
 
 Is that the one that shoots in the .3s and .4s, if not, what is that rifle built on?

Rick: Forget the WSM project, and keep your .300WM as it is. Order a NEW classic safari express in .458WM and don't mess with your other M-70. You can purchase a new rifle for less than $900, and won't have to screw around with the conversion. By the time you make all the necessary changes to your .300, you'll be out as much, or more than buying a new .458WM. I'll be more than happy to provide loads for the calibre which will give at least 2100fps with a 500gr. bullet. NO pressure problems either. (I have used my loads in Africa with temps in the mid, to upper 90'sF And as an aside, the last cape buffalo I whacked, the Trophy-Bonded solid broke the near shoulder, destroyed the lungs, and top of the heart before sailing off into the nether reaches of the Zimbabwe bush. Since the buffalo was running at the time I took the shot, he didn't realize he was dead, and carried on for about 50yds and fell over and gave his final moan.) As to weight; I believe the SG weight is right at 8lbs., the .458WM is about 8.5, which is a bit on the light side for any calibre above the .375H&H. INMO Anyhow, good luck with the project, whichever direction you decide. Sakubona, Mukiwa

don't overlook the fact that Winchester (custom shop?)
 will build you a nice .458 Lott, and ammo is now commercially available...
 
 Or you could pick up any .458WM, and do the conversion quite
 easily..
 
 so practice with .458WM, hunt with .458 Lott....

Mukiwa,
 
 I'd be interested in seeing your .458 WM loads!
 
 Eric

you guys are killing me I have a spare model 70 in 300 win mag going to waste. tom

Charlie Sisk---What is the feasibility of converting a short action (insert brand here) to .450 Marlin? I have seriously thought about a Savage short action due to the ease of changing the bolt head but another brand wouldn't be that much more work, would it?? Would this be a more readily available and economical conversion versus the Siamese Mauser/45-70? Either way, you would have a serious North American rifle.

Vic

Vic in VA
A short 300 WSM action will work with no modification. I built one for Wayne van Zwoll and it fed great. The Remington actions in SHort Ultra mag or the 673 ina 350 Rem mag should work also. They wont feed the blunt flat nosed bullets but the ones that are the least bit rounded feed fine. In my experience, the 450 feeds better that the WSM cartridges do. And you can really load that puppy up in a bolt gun..........<img src="/ubbthreads/images/graemlins/grin.gif" alt="" />
Charlie

Charlie--thanks for the reply. I had a suspicion that was the "case". I had a short-action Savage here I just sold, but was seriously thinking about that conversion. If I find another one, I just may do it.

The Savage I had was a .308, so changing the bolthead and magazine would have been necessary.

Makes me want to listen out for somebody with a shortmag they are no longer interested in. May have to wait awhile, though, them things is selling like hotcakes. That's why I was considering the Savage action. A couple of parts from Midway, and a barrel from somebody like Pac-Nor, and a-thumpin' we will go. I imagine that case will handle pressure in the mid-50 kpsi.

Thanks again and Merry Christmas---Vic