Now, I have yet to handle one so Im somewhat in the dark here, but what you have is a semi automatic rifle, that will handle .30-06 length cartridges, with a 4 round drop out magazine.  (With I believe after market mags that will hold more).


A .458 Winchester magnum was designed to operate in rifles of the .30-06 length, a 'short' magnum of the times.  Could a gunsmith rechamber your 7400 to .458 Winchester?  Would it survive the beating?  Would YOU survive the beating?


If I was rich, I would find out first hand.  Would it work?

I'm not a reloader, and I may be off track, but I think the .458 Winchester magnum needs a longer barrel lenth than the 22" found on the 7400s,  Chamber pressures seem to be about the same, but I think the .458 uses slower powders, and therefore needs the longer barrels to get max performance.  With chamber pressures about the same the 7400 SHOULD be able to handle it.  Edited- And the gas sytems not set up for that cartridge so it may not time the bolt opening correctly.

These guys do work on 7400s but don't offer that cartridge www.accuracysystemsinc.com/cust_remington_7400.html give'm a call and see what they say.

But personally, I wouldn't do it.

I don't think it would work, and here's why.  The main problem is the difference in the case head diameter.  The '06 is .473", whereas the .458 is .532"  The OAL of both cartridges still measure in at 3.340" each, which means theoretically the length of the cartridge would allow it to work in the 7400 action.   However, the amount of back thrust from the .532" case head awould be too much for the 7400 action.  Plus, you would have to mill out the bolt face on the 7400 bolt.  Unfortunately, the bolt face walls are all ready thin at .473, so milling to .532 would not be possible.  You would need a larger bolt, which would subsequently require larger receiver and larger barrel extension for the lugs on the bolt (which would also have to be bigger).  

So, I guess the answer to your question is no.  Unless, of course, you want to build a single receiver, bolt, and barrel from the ground up to accomodate the .458 Magnum in a 7400 style action.

Now, you could possibly rechamber a Browning BAR rifle, as they are factory chambered for the 7mm, .300 Win Mag and .338 Remington magnums.   Each of these rounds share the same case head diameter as the .458, so converting one would be possible.  I would think any competent smith could do it, but I would not guess it to be cheap.  You would need a custom barrel blank milled for the BAR, and regulated for the gas system.  

The only question is, why would you want a semi auto .458?  

For killin things that don't want to die!


Just feeling out a whim.  Also, it would shit stomp a bear.  (But a 12 guage with slugs can do the same thing)

Actually converting to 458 Win Mag could be done. The bolt face can be opened up from 0.473 inches to 0.532 inches on a LATHE not a milling machine. I have opened up many bolt faces from standard to magnum to accomodate customers rifle builds. The Rem 7400 is not a particularly strong action nor is it noted for its accuracy. Custom gunsmithing is an expensive process and the costs to convert from 30-06 to 458 would probably be higher than a simpler project such as a bolt action rifle standard to magnum conversion. Charles. Gunsmith.

Maybe on a bolt gun, where the walls of the bolt face are markedly thicker.  However, doing so on a 7400 would thin the walls too much.

www.browning.com/products/catalog/firearms/detail.asp?value=002B&cat_id=031&type_id=001 as already mentioned.

I'm guessing a 7400 wouldn't stand up very well to .458WM, if it could be done.

I've shot a couple rifles in 458WM, a Ruger #1H Tropical and a Savage Safari. 510 grain loads would turn a 7400 into kindling and metal shavings.

I miked the bolt face on a 7400 today, and its pretty close to the thickness on standard bolt guns.  However, the problem would still remain with back thrust, and the gun simply would not be able to hold up.  

So really, its a BAR question, would IT be able to take the beating.


That was my initial gun that made me ponder, but I didnt want to mess with a good Browning and blow it up

What about a Browning pump?  Those come in high pressure mags.  New barrel, custom mag, go shoot.

Excessive bolt thrust, to the rear, is caused by excessive headspace and or poor chamber cutting. This can be controlled. The sheer recoil produced by the cartridge firing a projectile weight of say 400 grains when comapred to a 30-06 at say 180 grains at equivalent velocities and chamber pressures would be very difficult to control. A secondary recoil lug system would probably have to be fabricated and the stock would have to be reinforced. A Browning BAR designed for a 300 win mag based cartridge would be a much stronger rifle to be considered for this kind of major project.

I believe the BAR has been converted to .458 Win.Mag. at some point.

McMann (?) Industries in WA STATE has converted M1 Garands to bigger magnum calibers.

I have a 7400 Carbine Synthetic and will leave it as is.  It's a good little rifle for hunting non-dangerous game or maybe OK for defense of North American Bears.  I wouldn't think of trying to make it a DRG Rifle, though.