7mm Rem. to .458 Winchester

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20 April 2013, 21:14

John55

7mm Rem. to .458 Winchester

I have a M70 classic in 7mm that I'm considering having rebarelled to .458 Winchester. Would the rails have to be opened up to get that cartridge to feed?
Thanks,
John

20 April 2013, 22:44

ramrod340

Shouldn't The 7mag is basically a necked down 458

21 April 2013, 00:10

Alberta Canuck

It MAY require tweeks to feed correctly, but the gunsmith doing the barreling won't know until he gets the chambered barrel fitted.

Although the 7m/m RM and the .458 WM use the same basic brass, the formed cases and their bullets are both significantly different in shape.

That means the cartridges of the two MAY need different feed ramp shapes in order to feed well. As there is basically no shoulder on the .458 WM, the fronts of the rails MAY also need to be slightly opened too.

21 April 2013, 00:10

PWS

I had this very conversion done recently on a stainless G17xxx series action and my 'smith used the newer SC mag box and follower and it feeds and functions like corn through a goose without touching the rails or feed ramp. The box has the relief "windows" in both sidewalls of the mag box and the follower is machined aluminum. It's a perfect stack for three .458WinMags.

21 April 2013, 00:15

dpcd

Model 70s don't have cartridge specific feed rails; all feeding is controlled by the magazine box lips. Most of them work on many different ammo types. I think there are only 3 or 4 variations of them. Boxes. Basically, you should be able to stuff and feed as is going from a 7 to a 458.

21 April 2013, 00:47

John55

Thanks,
That's what i was hoping to hear.

21 April 2013, 01:59

JBrown

quote:
Originally posted by Alberta Canuck:
It MAY require tweeks to feed correctly, but the gunsmith doing the barreling won't know until he gets the chambered barrel fitted.

I disagree. The 458 can be fed into the 7mm mag chamber to test feeding. Of course the bolt can't be closed, but that is unnecessary for the testing of feeding.

Just remove the firing pin assembly, then load the magazine with 458s(or better yet, use 458 dummies) and work the bolt back and forth just enough to get the cartridges into the chamber and onto the boltface. That will tell you if it feed feed and eject 458s without tweaking.

This was what I did with my 7mmRM Mark-X before having it rebarreled to 458. Feeding was slick before and after.

Jason

"You're not hard-core, unless you live hard-core."
_______________________

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