I need your thoughts on what will be involved to rechamber a M70 Extreme Weather SS from 338 Win Mag to 375 Ruger. I want to have the barrel rechambered and cut to the 375 Ruger but have never done this and need to lean on some experience here.

Both calibers have a rim diameter of .532. The 375 Ruger has a base diameter of .532 to.515 at the shoulder. The 338 Win has a base diameter of .513 to .491 at the shoulder. The 375 Ruger has a case length of 2.580 and a COL of 3.340 inches. The 338 Win has a case length of 2.50 and COL of 3.340 inches.

My questions are:

Will the barrel be large enough for a .375 bore? I cannot find any dimensions on their barrel or what manufacturer makes it. It is fluted and this may present a problem. Is a 1 in 12 twist optimum for this caliber?
How will the new cartridge feed with the 338 Winchester box? Will I need a new box and follower for the fatter Ruger case?
Will the rails need to be opened up for the fatter case? What about the ramp? Will it need to be opened up also to accomodate the larger bullet and fatter shoulder?
Since the fluting only covers 50% of the barrel would I have any problems mounting iron sights on this barrel.

I know I could just buy a Ruger rifle and get the caliber in a cheaper package but I want it in an M70. Besides I need a project and this idea keeps bouncing around in my head.

http://www.winchesterguns.com/...ail.asp?id=535110236

Sid

quote:

I know I could just buy a Ruger rifle and get the caliber in a cheaper package but I want it in an M70

First off, you should be given an "Award", and on top of it a "Promotion" at work, a raise to boot for the statement above!

If you know me, I would have it no other way, and if it would not work on a Winchester, well I can do without it, End Of Story!

Well I thought exactly like you a year or so, maybe 18 months ago, not real sure exactly, but I had a bunch of 300 Win, 7mm, 338s and such M70s hanging around with no job! So I wanted to do something with them, my B&M series based on RUM cases are too big for those rifles, magazine wise, we had already looked into that very seriously. Winchester I am told did a hell of a lot of changes in the M70 to fit the RUM cases, which they made a bunch of those in 300 RUM. Well I got my hands on some of the Hornady basic 375 Ruger brass, and Capoward and I decided this was the hot ass ticket for those 300s and 338s! It looked like it would work fine to both of us! I was not going to do a 375, but a 500 and I think Capo was thinking .423 or something. So I sent rifles up to SSK to Brian, does all my B&M work. He monkeyed with it for some time, and come to the conclusion that he could not promise these would retain and stay in the magazine. Retaining in the magazine is the #1 issue when you do something like this on a Win M70. Feeding is not an issue, that is easy, but keeping the other two cartridges down is a big deal, not so easy as just changing the box inside. We looked at that as well. Since Brian could not promise that it would work, and I am a demanding bitch when it comes to that, then we offed the project.

Later Capo got in touch with Mike Mike??? The guy that posts here a lot, good gunsmith, good gun builder, good rep, damn I never remember his name. Anyway, he said he thought he could do it without a problem. I don't remember if I sent him a rifle, dummies, and so forth, but after several weeks of Mike looking at it, he came back and stated that it might can be done, it might be expensive, and there was zero guarantees that it would be 100%, retaining! Pretty much the same story as Brian at SSK. Now, I shoot'em, they won't let me work on them as I do more destruction than good, but with both of them telling me that this might be ugly and not work anyway, then I gave up on that project.

I sure do have a hell of a lot of basic Hornady 375 Ruger brass, no headstamp on it, as I bought 700-1000 pieces of it, cause I just knew this was going to work! All still in the box!

It would work fine and would not be difficult at all to do what you want on one of the Winchester M70s that was chambered in 300 RUM. I keep several of these on hand, but they are all slated for 500 MDM cartridges.

That's about what I know about this! I am sure not exactly what you want to hear! I can tell you one marvelous thing you can do with that rifle however, being in 338. The rifle I sent up to Brian for him to look at was a 300 Winchester, same action and boxes as the 338, I had him change the barrel out, and do a 9.3X338 Winchester, and that is a nice nice cartridge. Same velocity as 338, only with .366 caliber bullets, my opinion a worth while boost for the same case. Easy to load and lot's of brass available too!

Michael

Thanks for the reply Michael and yeah you may have thrown a monkey wrench in that idea but that's why I asked first. My other thoughts were to rechamber to 340 Weatherby because I love that round but it can wait.

I really want to take one of those 500 MDM's off your hands but need to save up the $3800 plus dies and brass first. The reason I have been picking on less expensive projects is because I had an on the job injury and have not been cleared to go back to work yet. I will probably never ride my dirt bike again so maybe I will sell it for the funds. I have too much time on my hands ATM and I am trying to stave off boredom.

Maybe we should start a petition to FN to start chambering RUM cartridges again in the M70...I think they would sell like hotcakes. Thank You for the response.

Sid

Hey Sid, no thanks needed, but with two top notch guys not being able to guarantee retaining, then that's a bad sign. Capo may see this and help my memory some, but I think I am spot on.

Yeah, if you want one of the ones that I have for sale, you better speak as I already confiscated the GunKote finished rifle for myself! HEH HEH.... Who knows when the blue one may go too! LOL...... But the damned things are too big anyway! I think I am going to be messing with the 475 B&M some in my future adventures!

Sorry to hear about the injury! I know that is awful. The Big B in the B&M was throwing some trash in the damned dumspter the end of last week, tried to throw his arm in with it, pulled all out of whack, going for surgery on it next week, will be out of the shooting business for months on end! The older we get, the easier it is to get hurt I think! Always something it seems.

YEs, if Winchester (FN) in SC would start chambering RUMs again--HooRay! Maybe they start chambering the Rugers? That would work also! Maybe they should just start chambering the damned B&Ms--that would be easy as hell for them! They already have WSMs! Talk about a new big bore and different! I heard a rumor that they are thinking a big action too? Who knows these things?

Michael

Man I hope his surgery goes well and is more successful than mine was. I know the older I have gotten the slower I recover from injuries. It sounds like he may have damaged his rotator cup and that would be really bad indeed.

Hopefully he will still be somewhat active during his recovery. Being able to do some regular activities helps greatly with the mental aspect of recovery. I have been working on friends rifles and reloading a lot of rounds trying to maintain some sanity.

I also discovered the fun of Duracoat finishing firearms and whatever other likely candidate I can find. I even want to Duracoat my wife's Pekingese but not sure if the dog will survive the baking process. Would sure take care of the fur problem tho. Maybe I should experiment with the neighbor's dog first....damn thing barks all night.

Michael,
Mike Cuypers was the 2nd gunsmith, besides Brian, that looked things over and decided both the 500 MDM (375 RUM case) and the 50 MDM (375 Ruger Basic Case) were a no-go relative to converting one of your 300 WinMag’ M70s without spending quite a bit of money with no guarantee that it would function properly.

Sid,
My brain is malfunctioning right now so I can’t remember which gunsmith converted a M70 to 375 Ruger. Best of my recollection though…he used a M70 chambered in 270 Winchester as the base rifle because the rails are narrower (haven’t been opened up yet for a belted magnum cartridge) which allowed him to alter the rails to properly feed and retain the .375 Ruger cartridge. For the magazine box, I believe he used a .338 WinMag box with some modification for properly work with the .375 Ruger. It can be done…you just have to use the correct components first. Try running a search in the AR Gunsmith forum and perhaps you’ll find the reference…would have been 2009/2010 timeframe.

Michael,
Perhaps we should have discussed using a M70 chambered for a 270 Winchester.

You can rebore the rifle and a good smith can work over the action..I suggest Dennis Olson in Plains, Mt. I know he uses custom bottom metal from Blackburn, Grisel or whoever and he uses the .338 box for the 375 Ruger conversion. I shot one of his conversions and it fed perfectly and shot very well indeed..You might give Dennis a call. 406-826-3790 for his opinnion.

Thank You Ray. It's always good to hear from someone who has been there and done that. I had already started thinkinrg about a 375 Weatherby conversion but who knows. It does seem like the 375 Weatherby would be a much more affordable option tho.

Was it Jim Kobe who rebuilt a pre64 to handle the .375Ruger?

D'Arcy Echols built one for Zambian PH Athol Frylink as well and Athol speasks glowingly of it.

Michael,
Tell those Winchester people to make some of those WSM actions for us lefties! I'll buy at least one and maybe two. One, of course, to be made into a .475 B&M.

We took a M70 in .300 WSM and changed it to
.416 WSM. I have the dies and make brass from .300 wsm brass.I have a good load for it and it gets sub moa groups.
Now I no longer have a need for it, so it is for sale if your interested>

quote:

Originally posted by PWS:
Was it Jim Kobe who rebuilt a pre64 to handle the .375Ruger?

No! I did however take a Classic M70 and rebarrel it to a 375 Ruger. It was problematic in that it would no hold more than two down. Solution? I got some new bottom metal from Duane Weibe and installed it. I had to modify the action, open it up, to accept it but after that it would hold 4 down and fed great.

quote:

Originally posted by Jim Kobe:

quote:

Originally posted by PWS:
Was it Jim Kobe who rebuilt a pre64 to handle the .375Ruger?

No! I did however take a Classic M70 and rebarrel it to a 375 Ruger. It was problematic in that it would no hold more than two down. Solution? I got some new bottom metal from Duane Weibe and installed it. I had to modify the action, open it up, to accept it but after that it would hold 4 down and fed great.

My mistake Jim. Thanks for clarifying that it was a Classic. I read your conversion with interest but didn't go back to the original thread when posting the above. A "4 down" Classic in .375R would be a nice setup!

I have a 416 Ruger built on a Classic (NH) M70. I haven't added Duane's bottom metal or any other mods to magazine other than change out the spring for a 375H&H spring (w/o the goofy bend in it). Feeds well, but I haven't checked the 'retaining' other than to know that the rounds in the mag do not pop up and out when the bolt is pulled back.

4 down with Duane's bottom metal would be a nice addition if Jim is up to doing the necessary action mods . . . .

Another option and much cheaper than a drop box magazine is to use the standard 3 shot down magazine and a 3/8s inch floorplate milled out to help takes the 4th round. about $225 to $300 depending on who does the work. I really think one needs 4 down and 1 up in the 9.3x62, 9.3x64, the 375s, not so in the big 40 calibers but it still don't hurt.

My advice is to sell your M70 Extreme Weather in 338 and buy a stainless M70 Classic in 375 H&H, then have it CeraKoted if you're concerned about seriously wet / salty weather. It will be much cheaper and you will end up with a truly classic rifle. That being said, I wish Winchester would come out with an Extreme Weather 375 H&H, the M70 Classics are getting hard to find ...

I have not bought the Extreme Weather yet I was just kicking around the idea of converting one. I was thinking it would be a fairly simple job but that seems to not be the case. You know how it is sometimes you want something different.

I still like the idea of the 500 MDM tho. I have no real need for it other than proving my insanity to members of my hunting club. No I take that back......I really do need a heavy big bore to regain my sanity. Maybe it will knock some sense into me for once.

You'd be better off rechambering to .375 H&H Ackley Improved - more power than the Ruger.