Hey guys,
I'm thinking about converting a Winchester Model 70 Classic (New Haven) from 300 WinMag to 375H&H.

Notching the front ring and opening up the back of the receiver and punching in one more scope mounting hole seems fairly straight forward.

Since these rifles feed off of the receiver rails and not the magazine box, are there any tips to getting the rails right? Just duplicating what I see in a factory rifle would probably be fine, but I'm hoping someone might have some words of wisdom (sans snark, please).

Thanks!

Snark is what I do. Gets people's attention.
However, your question, I have done many times, and here is how.
All Model 70 post 64 receivers are already 375 length. Making them longer, and making them from forgings were two salient features of the post 64 model 70. Unlike pre 64 where they were all 30-06 length and needed receiver mods to accept the H&H, not so now.
All you need to do is alter the ejector blade, or buy a new shorter one.
Receiver is fine as is. Mag box will need the spacer removed; they are just spot welded in, so that is easy.
That's it. I have converted standard cartridge ones to 375 too; open up the bolt face.
I actually prefer the push feed ones; they feed smoother, and yes, still extract fine.

You are going to need to open up the loading port to get reliable ejection. you won't need to notch the front ring either.

I forgot to say chop off the bolt stop too. Or get a shorter one.

Friend converted my Classic 270 to 375H&H. Great rifle.

In modified D’Arcy Echols stock. Fabulous.

I recently had DPCD do a similar conversion for me. I bought a stainless, post '64 M70 ( Left Hand ) in 7mm Rem Mag which was rebarreled to .375 H&H. Also installed a longer magazine box, exchanged the two-piece bottom metal to one-piece, opened the ejection port and amended the bolt stop and ejector as described here by DPCD. He also ensured that action cycling ( feeding, extraction, ejection ) were flawless and sent me some video to show it cycled as required.
When I received the rifle in New Zealand I was very happy with everything except I found that action cycling resulted in quite heavy scoring of the brass. This was a concern as I handload, was concerned about brass longevity and wanted this issue addressed. Luckily we have here a very good gunsmith competent with CRF actions who identified the cause as the receiver feed rails which he corrected with a little judicious filing. This not only sorted the issue but made feeding feel much slicker as well.
Great result all round producing a very handy rifle.

Edit: ... AND repolished the feed ramp which no doubt contributed to the smoother feel of feeding ...

Ahhh Feeding isues...Can drive a gunsmith to tears!

The gunsmith can make it feed with any factory ammunition he has on hand. Customer loads his own and won't feed worth crap[.

Been through this few times. I'd guess the most common gremlin is seating the bullets out too far.

Next, bullet choice. CEB13 bullets can be a big problem. Loved by many hunters, hated by many gunsmiths.

For a double...great. A bolt gun ? Most times, NOT straight line feeding, exacerbated by corners on the bullet itself.

Had one rifle that would feed perfect on the horizontal, but would hang up occasionally if muzzle was pointed down.

Go figure!

Of course, most feeding issues are going to occur with a cartridge conversion, especially on big bores (Surprise, suprise)

quote:

Originally posted by Duane Wiebe (CG&R):
Ahhh Feeding isues...Can drive a gunsmith to tears!

The gunsmith can make it feed with any factory ammunition he has on hand. Customer loads his own and won't feed worth crap[.

Been through this few times. I'd guess the most common gremlin is seating the bullets out too far.

Next, bullet choice. CEB13 bullets can be a big problem. Loved by many hunters, hated by many gunsmiths.

For a double...great. A bolt gun ? Most times, NOT straight line feeding, exacerbated by corners on the bullet itself.

Had one rifle that would feed perfect on the horizontal, but would hang up occasionally if muzzle was pointed down.

Go figure!

Of course, most feeding issues are going to occur with a cartridge conversion, especially on big bores (Surprise, suprise)

I should have noted in my post above that from the outset with the calibre conversion it was intended that the .375 H&H would shoot my own handloads which are loaded longer than factory rounds and which DPCD took into calculation. So far with loads I have shot Barnes TSX 300gn, Barnes TSX 270gn, Woodleigh Weldcore RNSN 300gn, North Fork Semi Spitzer 300gn, North Fork Solid 300gn, North Fork Cup Point Solid 300gn, Hornady DGX 300gn and all have fed / cycled without issue.

DPCD is very accomodating,,,

Have one in the shop right now converting from a 30-06 to a 416 Ruger
Not a simple do this and presto as Tom would have you think for this caliber

Top half, barrel, bolt face and extractor all done, that's the easy part
Magazine box and rail guard re-work done, the harder part
Now am down to the final bit to make it feed smoothly, the hardest part
Also will have to make a new wider follower

Had to widen the magazine box .110" wider at the shoulder area so that fat case would lay in the box properly
Then re-machine the receiver to allow the wider box to fit inside

When I am all done it will hold 4 rounds in the magazine with room to spare and you can drop another cartridge in the chamber
Its headed to Africa next spring

James Wisner

Right; Ruger cartridges are fatter and are harder to make feed.
And we did use a wider follower and his custom ammo was Really long. Required some bridge milling to get it to eject a loaded round. I told him it would be easier to just shoot any round he chambered.
The reason King's rifle scratched his brass is that it was left handed. I couldn't make him learn to shoot normally!

Why not sell the .300 WM and buy a .375 HH???

That takes all the fun out of that; anyone can just buy one.
It's like hunting; why do you want to go into the woods and kill an animal for meat when you can just go to Kroger and buy it?

If we are talking about making sense then buying always makes more sense than building.
Fun factor aside, the cost of custom building something today is huge especially the custom stock portion off the build.
BB

Build vs Buy in this case is easy.

I already have the parts.

And, while I've never done this before, it's not terribly different from other things within my skillset, so figured I'd give it a try.

Darcy has a cool blog post on converting a 30-06 to 300 H&H (pre-64). I would be willing to bet there is a thing or two that may be of interest.

http://echolsrifles.blogspot.c...00-h-part-1.html?m=1

quote:

Originally posted by BaxterB:
Darcy has a cool blog post on converting a 30-06 to 300 H&H (pre-64). I would be willing to bet there is a thing or two that may be of interest.

http://echolsrifles.blogspot.c...00-h-part-1.html?m=1

For the astute student, those 3 blog posts are the keys to the kingdom.

quote:

Originally posted by DavidReed:

quote:

Originally posted by BaxterB:
Darcy has a cool blog post on converting a 30-06 to 300 H&H (pre-64). I would be willing to bet there is a thing or two that may be of interest.

http://echolsrifles.blogspot.c...00-h-part-1.html?m=1

For the astute student, those 3 blog posts are the keys to the kingdom.

Yup.

DE is converting a pre 64 action to 300 H&H; I thought the OP had a post 64 action he was starting with; none of the drama required to convert those; all post 64 actions are already H&H length. Pre64s are 30-06 length. I doubt if there is anyone actually doing this conversion in 2023. (Other than me!)
As for building vs buying; I always build.

Pre and post 64 M70’s all got built from the inside out like that in D’Arcy’s shop. Though the Post 64’s were machined for one of his proprietary cartridge specific magazine boxes.

It seems the general consensus is that the Botton half of the receiver doesn't need any work.

Then there are mixed comments about the top half, specifically if the rear bridge needs to be cut back to allow easier loading. I'll guess when you're doing this, you're also punching in that new ring screw hole and using the 'magnum' style rear base.

When cutting back the rear ring, how much overlap are you leaving between the ring and the rear of the extractor?

Bings back memories from a metalsmithing class taught by Tom Burgess at Susanville CA.

He claimed the pre 64 300/375's were heat teated seperately and differently at the factory..I recall he wasn't too keen on a conversion.

I had a wonderful 06 converted to a 300 H&H by Olson some years ago, shot it for years and on most of Africas Pg and a couple buffalo and a mad hippo..soldl it in a weak moment and Im sure thats no surprise to the AR tribe..feed like poop thru a goose, shot under an inch, sold on AR. would like to buy it back but can't recall who bought it! Its an age thangie demention I suppose..

I will have to see the documentation that the 375s were heat teated differently than other receivers. I can't think of any reason for that.
No, post 64s do not need any bridge mods. Come over and I'll show you 3 375s made from random calibers. Mostly 270s, which I like to destroy.

I've converted 3 Model 70 Laredo's to 375 length in the past 3 or 4 years. The first one only required mag stop and ejector shortening and replacement of the magazine box with a new .375 one to work. It took a bit of stoning and smoothing of the rails to make it feed right. And bending and polishing and working of the back of the mag box to make it load smoothly.

The second two were identical 300 win mags. They both required opening up of the feed rails for about 1/2 an inch back; the rails weren't factory done wide enough. I took photos of the process, but can't seem to find them to post.

And as Jim said, modification of the mag box and working the rails slightly to make it load and feed reliably were also required. 375 mag boxes have become unobtainium, so had to mod the last 2. First one I bought a 375 box.

Not a lot of work or a hard project, but not quite just shorten or replace the ejector and stop.

And remove the spot welded spacer out of the mag boxes. That is all I had to do; especially starting out with a belted mag, the rails are already good 1/2 inch at the rear. You must have got a reject; and I know it happens because I had to repair a new factory safety this week that would not engage at all. Can't believe no one noticed it.
As I said, come over and I'll show anyone three 375s I made from other calibers.
Here is one of my favorites; note that the barrel is a new CZ 375. Shoots great.

I personally never heard Tom Burgess say converting a 30/06 bolt faced Std length Pre-64 to a 300 or 375 H&H was a bad idea. In fact he told me more than once if done properly it was a better conversion to the receiver than Winchester did in New Haven with the original 300/375 design.

Heat treatment variations ? I've been trying to find one page in my notes pertaining to 10 Pre-64 receivers and bolts that I Rockwell (C) checked on a Calibrated Wilson Rockwell tester at one time in the late 80's. These were Pre-wars and post-war standard 270/30-06 receivers and Std 264-458 magnum receivers and a few 300 H&H receivers and bolts. It was interesting to note that they were all fairly consistent and much harder on the (C) scale than what you'd expect.

If you use a 270/30-06 receiver you can wind up with a longer feeding ramp (approx. .070) and a ramp angel less severe than the original 300/375 receiver. (think flat nose bullets) Unlike the original long mag you do not need a bullet nose cut out in the rear of the top ring and if done with some skill you will have a .030 thick radial flat on the lower lug bolt raceway, behind the recoil lug seat and at the top of the bullet ramp instead of knife edge which is all to common on the original 300/375 receivers.

You will need to remove metal (QUITE A BIT IN FACT) from the underside of the feed well, some use a Dremel, I prefer a Bridgeport.

You can loose the forward 6x48 screw hole in the rear bridge when you open up the ejection port, depending on how much you elect to open the port to the rear and will determine where you drill a new scope base hole. You can copy the original 300/375 configuration or............ Do want the tail end of the extractor to be lying just under the rear bridge or are you installing a longer extractor to obtain the same effect with a longer 3.600 ejection port ?

One of the real advantages when using 270/30-06 receiver is being able to establish feed rails cuts into a flame or Wasp waist shape. Wider at the rear of the rails to allow the belts to sit under the rails properly and allow enough of the case head to protrude above the rails for the bolt face to pick up properly. Then wider still towards the center of the rail length, then tapering and narrowing that width back down just behind and over the lip of the newly established bullet ramp. Look at a 33/40, VZ-24 or 1935 Chilean set of rails, Now I wonder why they did that on a 98 ?

You can now fit the longer 300/375 mag box into the 270/30-06 receiver so it fits like a latex glove instead of like an original 300/375 receiver and box, these can rattle around like a castanet.

Follower ? the 30-06 follower will usually not work as the forward nose will protrude up through the widened feed rails. Original 300/375 follower ?? better chance of working but you never known.

Bottom metal ? alter the length of the original bow ahead of the middle guard screw and you're good. Ejector length ? yes, needs to be shorter. Goes without saying the bolt face will need to be opened up correctly and the extractor lip modified as well.

Good conversion, bad conversion ?????? I've done more than a few and they're still in the field.

Conversion of a Pre-64 to a 375 Ruger that holds 4 in the magazine and 1 up ? now that's a project that takes a bit more time.