300 WBY to 458 Lott

1972RedNeck · March 18, 2025, 08:17 PM

I've had an itch for a 458 Lott for awhile. But I have zero need for one so I don't want to spend a lot of money on one. So I've been keeping my eye out for a cheap full length magnum in whatever caliber to have converted. Recently picked up a 1917 in 300 WBY for $385.

I already have a really nice Mauser 98 in 300 WBY that shoots well, but it's 1:12 twist and doesn't like bullets over 200 gr. Best trigger of any rifle I own.

My cheap 1917 has a 1:10 twist and shoots anything I can feed it quite well.

I suspected I would have this problem, but here I am:

The Mauser is off limits to mods. It may be the nicest/best rifle I own. But it won't shoot the heavies that I would like to from time to time.

I bought the 1917 with full intentions of having it converted to 458 Lott. It's a little rough around the edges and has plenty of character marks. But it flat shoots - jenesequa is the only way to describe it. I am having a really hard time modifying it just because it shoots so well.

So which do I convert? Or just let them both be and find another project rifle to modify?

105kw · March 19, 2025, 12:12 AM

I would not want to convert a good shooter to another caliber.
My vote is find another rifle for rechambering, and don't shoot it for accuracy before rechambering.

stagpanther · March 19, 2025, 03:19 AM

If it were me--I would be far more concerned about how the rest of the rifle was constructed to sustain the battering-ram impacts of the Lott than simply what barrel you have screwed on.

**44 AMP** · March 19, 2025, 08:00 PM

Quote:

So which do I convert? Or just let them both be and find another project rifle to modify?

Any time you get a built rifle for a project, you "run the risk" that the rifle as is, has some useful and beneficial shooting characteristics, as is. I have seen rifles with bores that looked like plowed fields and still shot well. Not often, mind you, but it can happen. Sometimes rarely, but sometimes something that looks like a junker still has valuable life left in it.

The only way to be certain to avoid that sad state of affairs

is to start with an unbuilt rifle.

Jim Watson · March 19, 2025, 10:42 PM

If you don’t take the .300 barrel out with a pipe wrench and if you don’t have to grind out the feed rails for the straight case, you could go back.

A common recommendation.

Nathan · March 20, 2025, 06:20 AM

A Win 70 Safari Express is somewhat available in 458 win mag. This converts to 458 Lotto relatively easily. If I remember right, $ to ream, bedding and I wanted tome sight work and barrel shortening. It is also more of a classic style. It has a second recoil lug to bed built in and cross bolts.

The problem with low caliber conversions is how do you handle the recoil? 458 Lott has a rep for cracking stocks. That M70 stock is a bit more wood in all the right spots.

1972RedNeck · March 20, 2025, 10:49 AM

Does a model 70 in 458 Win actually have the full length magnum action? I was under the impression that only the 375 H&H models did?...

stagpanther · March 20, 2025, 01:23 PM

Well you could, maybe, get your hands on a 458--338LM reamer (I read someplace on-line that D Kiff at PTG once made one) and make your own 458 that's somewhere between the Lott and Rigby.

I'm a big fan of the 338 LM and Lapua's brass is tough stuff. I'd stick it on a modern all metal chassis. The only question would be would any guide be caught out in the bush with a customer carrying a rig like that LOL. Just thinking creatively.

taylorce1 · March 21, 2025, 08:26 AM

What kind of Mauser is your .300 WBY? If it is a commercial Mauser and it doesn't shoot the way or the bullets you like, I'd rebarrel it. Just get the barrel contoured to match your current contour so it fits your stock inlet the same. There are also some gunsmiths have the ability to rebore a barrel. So you have options.

There is a really nice custom Van Horn 1917 .458 Lott on Gunbroker for $6500, that offers layaway. Then there is a Ruger 77 or CZ 550 that can be had for about half that price or less. Both of those would probably be cheaper in the long run than finishing one of your existing rifles.

I converted a M70 7mm Rem Mag to .375 Ruger because it was far more affordable than making it a .375 H&H. It has taken more than 10 years to get it to the point I'm at now and over $2000 invested. Most of it is in labor getting the stock shaped from a wide oval forearm with a hooked pistol grip, to a more traditional looking hunting stock.

I've also finished a 1917 sporter in .300 H&H that have a little over $1000 into it, and all I did was restock the rifle, add a Timney Trigger, and a scope base. When I bought the 1917 it was already chambered in .300 H&H, the feed work was done, trigger guard had been straightened, and the rear bridge had been reworked with the ears ground off.

**44 AMP** · March 21, 2025, 03:54 PM

Quote:

Does a model 70 in 458 Win actually have the full length magnum action? I was under the impression that only the 375 H&H models did?.

My information is that the Winchester Model 70 .458 Win Mag was built on the same action as their .375 H&H. It is their long action, just chambered for a cartridge shorter than the H&H one.

Any action chambered for the .375 H&H is long enough for the .458 Lott. The Lott is, essentially, a .375H&H case, blown out nearly straight (there is a slight taper from case base to mouth, but no real shoulder in the usual sense).

1972RedNeck · March 22, 2025, 10:21 AM

So the model 70 in 458 Win has the same amount of bolt travel as in 375 H&H? Or is just the reciever opening the same and the bolt stop needs reworked? What about the magazine box length?

**44 AMP** · March 22, 2025, 01:45 PM

The specs for max loaded length for the .458 Win 3.340" and 3.600" for the .375 H&H.

That's a whopping 0.26" difference, essentially 1/4 inch.

Sorry I can't help from personal experience, my only model 70 is a .22-250.

You need to find a Model 70 in each caliber and measure them to be sure.

Personally, I doubt Winchester did anything to the bolt stop or magazine box to make the action fit the shorter round more closely. It's literally wasting money for a quarter inch that the buying public likely wouldn't even notice, much less care about.

1972RedNeck · March 22, 2025, 04:38 PM

From what I can find, a 458 Lott in a M70 needs an "express length" action with is a long action with the receiver opening milled a little longer. Takes different scope bases because they had to move the mounting holes closer together. They also get a longer mag box.

I know for sure that new 375 H&H and 416 Rem M70s are express length actions. I don't know if the 458 is or not and none of the gun stores within 100 miles of me have one.

Nathan · March 23, 2025, 12:54 AM

Mine was bought as a 458 Win Mag and I didn't pay for any mag work when it was converted to 458 Lott.

March 18, 2025, 08:17 PM	#1
1972RedNeck Senior Member Join Date: December 8, 2015 Posts: 379	300 WBY to 458 Lott I've had an itch for a 458 Lott for awhile. But I have zero need for one so I don't want to spend a lot of money on one. So I've been keeping my eye out for a cheap full length magnum in whatever caliber to have converted. Recently picked up a 1917 in 300 WBY for $385. I already have a really nice Mauser 98 in 300 WBY that shoots well, but it's 1:12 twist and doesn't like bullets over 200 gr. Best trigger of any rifle I own. My cheap 1917 has a 1:10 twist and shoots anything I can feed it quite well. I suspected I would have this problem, but here I am: The Mauser is off limits to mods. It may be the nicest/best rifle I own. But it won't shoot the heavies that I would like to from time to time. I bought the 1917 with full intentions of having it converted to 458 Lott. It's a little rough around the edges and has plenty of character marks. But it flat shoots - jenesequa is the only way to describe it. I am having a really hard time modifying it just because it shoots so well. So which do I convert? Or just let them both be and find another project rifle to modify?

March 19, 2025, 03:19 AM	#3
stagpanther Senior Member Join Date: March 2, 2014 Posts: 12,968	If it were me--I would be far more concerned about how the rest of the rifle was constructed to sustain the battering-ram impacts of the Lott than simply what barrel you have screwed on. __________________ "Everyone speaks gun."--Robert O'Neill *I am NOT an expert--I do not have any formal experience or certification in firearms use or testing; use any information I post at your own risk!*

March 20, 2025, 01:23 PM	#8
stagpanther Senior Member Join Date: March 2, 2014 Posts: 12,968	Well you could, maybe, get your hands on a 458--338LM reamer (I read someplace on-line that D Kiff at PTG once made one) and make your own 458 that's somewhere between the Lott and Rigby. I'm a big fan of the 338 LM and Lapua's brass is tough stuff. I'd stick it on a modern all metal chassis. The only question would be would any guide be caught out in the bush with a customer carrying a rig like that LOL. Just thinking creatively. __________________ "Everyone speaks gun."--Robert O'Neill *I am NOT an expert--I do not have any formal experience or certification in firearms use or testing; use any information I post at your own risk!* Last edited by stagpanther; March 21, 2025 at 03:40 AM.

March 21, 2025, 08:26 AM	#9
taylorce1 Senior Member Join Date: November 18, 2005 Location: On the Santa Fe Trail Posts: 8,498	What kind of Mauser is your .300 WBY? If it is a commercial Mauser and it doesn't shoot the way or the bullets you like, I'd rebarrel it. Just get the barrel contoured to match your current contour so it fits your stock inlet the same. There are also some gunsmiths have the ability to rebore a barrel. So you have options. There is a really nice custom Van Horn 1917 .458 Lott on Gunbroker for $6500, that offers layaway. Then there is a Ruger 77 or CZ 550 that can be had for about half that price or less. Both of those would probably be cheaper in the long run than finishing one of your existing rifles. I converted a M70 7mm Rem Mag to .375 Ruger because it was far more affordable than making it a .375 H&H. It has taken more than 10 years to get it to the point I'm at now and over $2000 invested. Most of it is in labor getting the stock shaped from a wide oval forearm with a hooked pistol grip, to a more traditional looking hunting stock. I've also finished a 1917 sporter in .300 H&H that have a little over $1000 into it, and all I did was restock the rifle, add a Timney Trigger, and a scope base. When I bought the 1917 it was already chambered in .300 H&H, the feed work was done, trigger guard had been straightened, and the rear bridge had been reworked with the ears ground off. __________________ NRA Life Member

March 22, 2025, 01:45 PM	#12
44 AMP Staff Join Date: March 11, 2006 Location: Upper US Posts: 30,484	The specs for max loaded length for the .458 Win 3.340" and 3.600" for the .375 H&H. That's a whopping 0.26" difference, essentially 1/4 inch. Sorry I can't help from personal experience, my only model 70 is a .22-250. You need to find a Model 70 in each caliber and measure them to be sure. Personally, I doubt Winchester did anything to the bolt stop or magazine box to make the action fit the shorter round more closely. It's literally wasting money for a quarter inch that the buying public likely wouldn't even notice, much less care about. __________________ All else being equal (and it almost never is) bigger bullets tend to work better.

March 19, 2025, 12:12 AM	#2
105kw Senior Member Join Date: June 30, 2017 Location: Columbia Basin Washington Posts: 516	I would not want to convert a good shooter to another caliber. My vote is find another rifle for rechambering, and don't shoot it for accuracy before rechambering.

March 19, 2025, 10:42 PM	#5
Jim Watson Senior Member Join Date: October 25, 2001 Location: Alabama Posts: 19,185	If you don’t take the .300 barrel out with a pipe wrench and if you don’t have to grind out the feed rails for the straight case, you could go back. A common recommendation.

March 20, 2025, 06:20 AM	#6
Nathan Senior Member Join Date: July 1, 2001 Posts: 6,825	A Win 70 Safari Express is somewhat available in 458 win mag. This converts to 458 Lotto relatively easily. If I remember right, $ to ream, bedding and I wanted tome sight work and barrel shortening. It is also more of a classic style. It has a second recoil lug to bed built in and cross bolts. The problem with low caliber conversions is how do you handle the recoil? 458 Lott has a rep for cracking stocks. That M70 stock is a bit more wood in all the right spots.

March 20, 2025, 10:49 AM	#7
1972RedNeck Senior Member Join Date: December 8, 2015 Posts: 379	Does a model 70 in 458 Win actually have the full length magnum action? I was under the impression that only the 375 H&H models did?...

March 22, 2025, 10:21 AM	#11
1972RedNeck Senior Member Join Date: December 8, 2015 Posts: 379	So the model 70 in 458 Win has the same amount of bolt travel as in 375 H&H? Or is just the reciever opening the same and the bolt stop needs reworked? What about the magazine box length?

March 22, 2025, 04:38 PM	#13
1972RedNeck Senior Member Join Date: December 8, 2015 Posts: 379	From what I can find, a 458 Lott in a M70 needs an "express length" action with is a long action with the receiver opening milled a little longer. Takes different scope bases because they had to move the mounting holes closer together. They also get a longer mag box. I know for sure that new 375 H&H and 416 Rem M70s are express length actions. I don't know if the 458 is or not and none of the gun stores within 100 miles of me have one.

March 23, 2025, 12:54 AM	#14
Nathan Senior Member Join Date: July 1, 2001 Posts: 6,825	Mine was bought as a 458 Win Mag and I didn't pay for any mag work when it was converted to 458 Lott.