I recently replaced my Win #70 Classic Super Express .375 barrel with a factory take off .458 barrel. It's headspaced and ready to go except for magazine/follower/spring changes or modifications. What needs to happen to the magazine to accomodate the caliber change?

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Phil- Life Member NRA & SCI

I don't think much, if anything, is necessary. I would just try feeding the .458 ammo from the magazine through the action.

Try it at a medium pace, then try it at a brisk pace. That should tell you what you need to know.

George

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"Shoot straight, shoot often, but by all means, use enough gun!"

If the CRF isa big issue for you, then you would need the bolt stop and ejector from teh 458 or 300 Win action and the magazine block.

The reason is that when you pull the bolt back and the cartridges have been driven forward by recoil, the bolt will expose the cartridge in the magazine before it has ejected the case in the extractor.

Push feeds with spring loaded ejectors do have some advantages

You might also consider rchambering that barrel to 458 Lott since your action is already set up for the 375 length cartridge

Mike

GeorgeS,
It feeds OK both fast and slow but has a tendency for the top cartridge to occasionally "pop" out of the magazine, front end first. When I insert 3 rounds in the magazine with the bullets close to the front of the box, things go down hill, as suggested by Mike375's post.

Mike375,
Will the .458 Lott feed well from the existing .375 mag box? It does seems a waste of magazine space and oal capability to stay with the .458 Win Mag.

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Phil- Life Member NRA & SCI

[This message has been edited by Phil R (edited 05-24-2002).]

Phil,

I don't know.

Why not make up some 458 Lott dummy rounds and see if they will feed with the 458 barrel on. They will go far enough into the chamber to tell.

There is a member here on the forum (a gunsmith) called John Ricks who has successfully done M70s in 458 Lott.

Cartridges like the 458 Win and 458 Lott with blunt bullets are always more critical for feeding because the bullet is not mucg smaller than the rear of the chamber and it the cartridge comes out of the magazine but just not right, then the bullet cactches on the chamber.

Mike

Thanks Mike 375. I'll talk to John Ricks.

Make sure the magazine box is straight at the top and is not bent in to make "lips".

The feed ramp likely will have to be widened to a broad "U" shape. 375's feed fine with a narrower ramp than the 458's, so you gotta open the ramp up.

Check the rear of the magazine opening in the receiver. There is often a radius at the upper rear corners that interfers with the case rim and belt when loading. I file it out square and smoth the sharp edges.

Sometimes have to open the distance between the front of the "rails" for good feeding, caution, take out too much and you have a junk receiver. Don't go to far back, about 1/3 the opening is usually enough. Be very careful here, lots of trial and error.

The top cartridge poping out early is a symptom of a feed ramp that is not wide enough. Can also be caused by a too narrow magazine, or bent lips as mentioned above. Or can be due to the magazine opening not being deep enough in the receiver, think of the lips being too thick in a vertical direction. With a stripped receiver, hold a round up against the bottom of the rails. The rim should stick up high enough for the bolt face to engage it and push the cartridge forward and out of the magazine. I taper the lips to match the cartridge diameter. Push a dummy round into the chamber mouth and watch how it feeds. You can see copper smears on the ramp and get an idea of how the ramp is steering the cartridge. Try this from both left and right sides. The worst offenders for poor feeding are broad nosed bullets.

Look at the bolt face and extractor. The extractor lip should have a nice smooth bevel for the rim to slip under. The lip around the bolt face, opposite the extractor, should have a good angle for a "funnel" entry of the rim. Check both with the bolt out of the action, slip a case up under the extractor. The extractor should also hold a loaded cartridge against the opposite side of the bolt face lip, and in a straight line with the bolt axis.

When I convert a M70 to a Lott, if it is not already the 375 length, I install the 375 magazine & follower, shorten the ejector and bolt stop, mill the rear bridge for a longer port opening, tap for 8-40 screws, work over the feed ramp and rails, and a few other minor items. The M70 magazine box is wide enough for up to a 404 case diameter. Some of the newer M70 375 boxes have dimples in the sides of the box, if yours has them, you need a box without this feature.

With the above modifications, you can make a Lott out of the 458 Win by running in a chamber reamer. If you elect to do this, be sure to use a Lott reamer ground for a 2.85" case length, most Lott reamers are for a 2.80" case. There is some brass running around for the Lott that is 2.83" or longer, will not work in the 2.80" chamber.

[ 05-27-2002, 06:59: Message edited by: John Ricks ]

WOW!! Good job of talking me out doing the job myself and having you do it, John! I'll get your phone # from your web page and give you a call.
Thanks.

John,

Would expect 375 Ultas to feed OK from an unaltered Model 70 375, in a particular the M70s before the change to the narrower magazine and followere with the scoop out of the middle.

Mike

I have replaced the .375H&H magazine box, spring and follower, bolt stop and ejector with "long" action parts and things work well except that cartridges from the left side of the magazine go to the right of the chamber when loading and the right side of the bullet, 350gr Speer FP, hits at the extractor cut out.Right side cartridges chamber real nice.

Does the .458 use a different follower than the .300, .338,etc? Brownell shows a .458 follower in their Winchester parts list, but it is way short of the long action follower and obviously mislabeled. So far, Brownells hasn't been able to answer my question.