300 WM Dangerous game calibre rebarrel (Advice Welcome!)

[Aiden204]

Bottom metal, even used, is hundreds of dollars.

Thread 'Mauser 98 .375 H&H Bottom Metal'

Apr 30, 2025

I’ve got a pretty nice trigger guard and hinged floor plate not being used, and I’m sure someone on here can put it to work. I believe this was originally from a Remington 798. It is all steel and gloss blued. The magazine box was factory extended to 3.7 inches and it was originally designed to stack .375 h&h. Let me know if I missed something, or you need more measurements. Im located in the D/FW metromess.

$275 shipped to an established member (and a bit less if you’re local)

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• Replies: 3
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New Blackburn will be $500 US, unfitted, unblued, may or may not fit your stock, action will have to be modified to work with it. It i$ po$$ible, but you will pay for it.

I cannot imagine a gunsmith charging less that $1000 to convert a std length 98 to accept the longer cartridges.

For the rifle you already have in hand, your most realistic choices are the 416 Taylor or the 425 Express.

ideally id find a 375, but finding a lefty action has unfortunately proven difficult. I got the rifle for $500 USD, a farcry from the $1500 being asked on GunsInternational for the same rifle.

Even if it ends up costing thousands (which I'd assumed it would) I'm ok with that. Its still much less costly than a new Production Parkwest or used Montana.

 

[Delloro]

ideally id find a 375, but finding a lefty action has unfortunately proven difficult. I got the rifle for $500 USD, a farcry from the $1500 being asked on GunsInternational for the same rifle.

Even if it ends up costing thousands (which I'd assumed it would) I'm ok with that. Its still much less costly than a new Production Parkwest or used Montana.

Well then, you have many choices!

I would start by finding a reputable, experienced gunsmith, and work out the caliber with him.

416 Rem would be an easy choice, but if the smith could do a Rigby or a Jeffery for the same money, that would be a tough decision for me.

 

[Aiden204]

Well then, you have many choices!

I would start by finding a reputable, experienced gunsmith, and work out the caliber with him.

416 Rem would be an easy choice, but if the smith could do a Rigby or a Jeffery for the same money, that would be a tough decision for me.

I originally was set on 458 Lott, now Im thinking perhaps 404 Jeff. theres currently 4 boxes of factory ammo (Brass without importing, yay!) in Country and dies available as well. it seems like a good balance of larger calibre & recoil

 

[Aiden204]

Well then, you have many choices!

I would start by finding a reputable, experienced gunsmith, and work out the caliber with him.

416 Rem would be an easy choice, but if the smith could do a Rigby or a Jeffery for the same money, that would be a tough decision for me.

here is the Zastava LK M70 in 9.3x62 (the standard mauser action, listed with a internally smaller magazine box) with a 458 WM round in the box. its quite tight but fits withought touching on the front. This leads me to believe 375, (therefore perhaps 458 lott?) 416 rem mag & 458 wm should fit in the magnum action no problem, as its box is listed at 93.7mm. can anyone let me know if I'm correct in this assumption?

 

[Badboymelvin]

425 Express would indeed be quick and easy. Also has the advantage of belted case with shoulder vs 404J has no belt and very tapered shoulder ( = tricky headspace). Ballistically it's supposed to be same as 404 and uses the same bullet. The downside is headstamped brass is almost nonexistent. That can be a problem if going to Africa with the gun. Using 300 Win brass doesn't match the gun and that can be a problem ... if the airport cops actually bother to look at headstamps.

When loading for my 425 Express I used Hornady, belted, un-formed brass which had no Headstamp.

This brass was then sent to a gunshop and they stamped (lasered?) the Headstamp on.

Maybe that's an option?

 

[Badboymelvin]

I would think getting the feeding rails just right for a straight taper case like 425 Express would be tricky. It's the reason why Jeffery Co went with sloping shoulder when they designed 404. The more constricted shoulder area of feeding rails helps ensure cartridges feeding from magazine make that final jump onto the bolt face at the right time/place. I suspect this is the reason why 500 Jeffery CZ rifles from the factory very often (universally?) have feeding issues. It took me almost three days gently carving on the extractor, rails, ramp, and follower before my 8mm Mauser action would reliably cycle 404 cartridges. Finally, I had to relieve some spring tension on extractor and that got her over the hump. Two gunsmiths told me that build was impossible but I knew Jeffery had done it. Standard action 98 Mauser was all they had to work with when cartridge was designed. Dennis Olsen even refused to tackle modifying the rails etc. But he may have been too busy. Getting the feeding right is an art form for sure. Remove too much metal and the action becomes expensive scrap metal.

I guess the one slight/maybe drawback to 425 Express is its belted case. Sometimes belted cartridges don't stack and/or feed as smoothly as non-belted. Or so the story goes. My experience is limited. I only shoot 30-06 and 404. Both are not belted. Most modern magnum designs have now dropped the belted design (e.g. Winchester WSM and Remington RUM were both designed from 404 case ... almost ... both have slight differences in rim diameter).

I've never had a problem with feeding in my rifle, although mine is a custom rifle and I'm not sure what work was done to make it like that...
But it can be done

 

[Pheroze]

One other possibility is a 400 H&H. You could make it .410 to share the same bullets as the 450/400 but with more giddy up.

 

[rifletuner]

When my son was 16, he decided he wanted a large calibre rifle for all the buffalo hunts he had planed in the future, plus he thought it would be fun to carry it around the hills for the occasional sambar hunt here in Victoria. He did a lot of research online, plus he read through a lot of the big bore rifle books I have on the bookshelf, and decided he wanted a 458 Winchester. I thought he made a pretty mature and well reasoned decision selecting that cartridge.

So I started looking for components for the build. We found a left hand Zastava M70 in 300WM which I bought as the basis for the build. I stripped off the barrel and stock and sold them off, just leaving me with donor action for the project. I ordered a Walther pre-chambered chromoly barrel and used the original magazine and bottom metal. The 458 Win Mag Feeds fine from that.

 

[Aiden204]

When my son was 16, he decided he wanted a large calibre rifle for all the buffalo hunts he had planed in the future, plus he thought it would be fun to carry it around the hills for the occasional sambar hunt here in Victoria. He did a lot of research online, plus he read through a lot of the big bore rifle books I have on the bookshelf, and decided he wanted a 458 Winchester. I thought he made a pretty mature and well reasoned decision selecting that cartridge.

So I started looking for components for the build. We found a left hand Zastava M70 in 300WM which I bought as the basis for the build. I stripped off the barrel and stock and sold them off, just leaving me with donor action for the project. I ordered a Walther pre-chambered chromoly barrel and used the original magazine and bottom metal. The 458 Win Mag Feeds fine from that.

I may end up just going 458 WM as its one of my favourite cartridges. awesome to hear it feeds good. So just a new barrel and you were set? no minor tuning or adjustment required!? Beautiful rifle amd glad to hear others have done the same as I'm doing with the lefty Zastava!

 

[Schüler Jumbo]

The .425 Westley Richards would be an interesting Classic.

 

[RedTag]

I may end up just going 458 WM as its one of my favourite cartridges. awesome to hear it feeds good. So just a new barrel and you were set? no minor tuning or adjustment required!? Beautiful rifle amd glad to hear others have done the same as I'm doing with the lefty Zastava!

Another vote for .458 Winchester Magnum. This seems to be the most straightforward and cost effective option. I had a Zastava 7mm RM and strongly considered re-barreling to .458 WM, but decided I’d rather save the money for another pre-‘64 Winchester. You could of course choose a longer and/or fatter cartridge, and the requisite gunsmith work to make it all fit. But the Zastava is a budget friendly rifle and as such I would keep any custom work on the budget friendly end.

 

[CoElkHunter]

E

Anything can be done with enough money and time.

Your rifle is set up for "short" magnum cartridges (magnum bolt face, .30-06 length action) so the .458 win family of cartridges will be the easiest to rebarrel to. They will only require a barrel and maybe some feed lip work.

.458 win
.416 ruger
.416 Taylor

Except the .416 Ruger case is wider so may require some modifications.

 

[CoElkHunter]

View attachment 732619
here is the Zastava LK M70 in 9.3x62 (the standard mauser action, listed with a internally smaller magazine box) with a 458 WM round in the box. its quite tight but fits withought touching on the front. This leads me to believe 375, (therefore perhaps 458 lott?) 416 rem mag & 458 wm should fit in the magnum action no problem, as its box is listed at 93.7mm. can anyone let me know if I'm correct in this assumption?

With my .375 H&H Interarms Whitworth (Zastava), the bottom of the feed ramp was cut at the factory to accommodate the longer cartridge. Works well and feeds and cycles flawlessly, but that’s what has to be done in that action for any cartridge longer than a “standard long action” cartridge like the .458 WM, because the Zastavas are not magnum length actions. My .416 Taylor Interarms Whitworth custom is a great shooter. Just get a Douglass .416 Taylor chambered barrel for your Zastava and you’re good to go if you want a .416. No rail or magazine modifications needed.

 

[Doug Hamilton]

howdy fellas. I hope this is posted in the correct thread. I recently picked up a Zastava LK M70 at a gunshow & was incredibly impressed with it. Upon further research I realized these guns came left handed. After a week of searching one popped up for sale here in Canada and I quickly purchased it. It's chambered in. 300 WM


My question is on the topic of Barrel Rechambering. I'm not overly sure on what calibre to pick? Ideally I'd like 458 Lott but I'm not sure how easily that will be done as I do not know if the magazine will fit the longer OAL of the 458 Lott Specifically. (if anyone has one handy and can measure that would be great)

I'm not a recoil sensitive person, in fact I'm becoming quite the fan of the "larger" calibres.

currently my collection is as follows
Zastava 9.3x62
Pre 64 Model 70 in 375 H&H
Double rifle in 450/400 3inch NE
Custom 458 WM
BRNO ZKK-602 in 500 A Square.

The gaps in my collection are obviously the lack of 416 (Although 450/400 is. 410) & anything between 458 WM & my 500.

is there an easy choice for a calibre to pick that won't be a huge pain to chamber in this rifle? Oddball stuff is ok assuming the reloading components are available in the US. I'm in Canada but regularly import

What about a .416 Ruger? I think the dimensions are right without having to do too much cutting on the extractor or lengthening the magazine box.

 

[Hsk]

Killer score on that rare lefty Zastava LK M70 in .300 WM those actions are tanks factory offered 'am in .375 H&H and .458 WM, so plenty strong for big stuff.

Real talk on rechambering

458 Lott is a stretch case is 0.3" longer 2.8" vs 2.5", OAL 3.6" vs 3.34". Your .300 WM mag box is standard magnum length 3.34" internal, so Lott rounds won't fit feed from the mag without opening rails feed ramp major gunsmith work, unreliable. Single load possible but defeats the purpose. Skip unless you want a project.

Easiest no drama options that drop in just rebarrel chamber, open bolt face, minor rail tweaks

.458 Winchester Magnum Factory did it, mag fits perfect, brass bullets everywhere US Canada easy. Gives you that step up from your custom .458 WM without gaps. Recoil beast but you love big kick.
.416 Rigby Classic gap filler between .375/.458, mag length works same as .375 H&H base, components available Norma brass, Woodleigh bullets import fine. Deep penetration monster.
.357 H&H Super easy factory caliber, belts feed smooth, ammo brass cheapish, bridges your Pre 64 perfectly.

I'd go .458 WM fills your between .458 WM and .500 ASq spot wait, you said lack between 458 WM & 500, but this is right there with more velocity. Or .416 Rigby for the true missing link your 450/400 covers .41 ish, but Rigby's a hammer.

 

[Challer]

What will the 416 do that the 458 or 450/400 won't?

 

[Schüler Jumbo]

Squeeze in a .500 Jeffery and be done with it!!

 

[Aiden204]

Squeeze in a .500 Jeffery and be done with it!!

500 A Square is way better than 500 Jeff imo, and I already have an A square

 

[Aiden204]

What will the 416 do that the 458 or 450/400 won't?

shoot a different calibre

 

[Arac]

I was looking at doing something similar and found that K.S. Arms in Edmonton makes both chromoly and SS barrels in .416 and .423 for CAD$575. They charge CAD$525 for re-barreling- threading and fit to action, chamber, crown, and caliber engraving.

They have a good reputation on other Canadian forums.

Good luck with the project!