Good Day All,

Just want to find out, has anyone ever converted a Ruger M77MkII from 7mm Rem to a 300 H&H?

I have a spare ruger action lying around and would like to know what to do with it.

Unless one has a ton of 300H@H brass and no 300WM brass.

Why would one go to the trouble.

But then gun cranks are not know to be practical all the time.

It can be done - there's at least one floating around in 375hh

The answer is Yes, but...
The mag box is 3.4 inches, so you will need another one to accommodate a 3.6 round. No problem there,
Mill out the receiver a bit.
However you will have to make a new bolt stop because the original is very thin and will not allow modification for longer bolt throw. Not a complicated piece though; easily made on your mill. Go for it. Post pictures.
But since I got to know the 376 Steyr, I just use those now.
Oh, you want a 300; not a 375. Just go with the Win Mag.

I think the best move is to go with the original 300 magnum; that would be the 30 Newton. It is the right length and size for the action and is a damn fine cartridge. If Winchester had chambered it in the Model 54, we would never have seen the H&H on this continent. Regards, Bill

Or, that extra action might make a good paper weight and you can spend your time on something more productive.

When Bill Atkinson modified a MKII 338 Win for 375 H&H for Bill Ruger he simply replaced the sheet metal magazine box and cut the factory bolt stop as thin as he deemed necessary.
It does look pretty thin but has held up quite well to a lot of heavy use. I attribute a lot of that to the excellent design of using bolt stop spring to buffer the impact. On well polished actions that same spring also make for a rapid bolt throw by initially starting the forward motion of the bolt.

Although I think the eventual development of the 375 Ruger was a wiser and better design for the standard MK II

If you want to do a .30 cal. magnum, and don't particularly want a .300 Win Mag and want something a bit different, think about the .30/338.

I have that new reamer for sale too.

Thanks for the replies!

To answer some questions:

1. I have 2x 300 win mags already.

2. Wildcats are unfortunately out of the question as based in South Africa, access to components is not easy.
3. It functions very well as a current 7mm. I like how the rifle handles and feeds. Unfortunately it has a bad barrel.


Any other suggestions calibre wise for a simple rebarrel job? This is just something fun and to pass time.

Is there anyone in RSA that does reboring of rifle barrels? if so, that would be an economical way to a 300 or 338 Win mag. Of course, this depends upon what is wrong with your current barrel. I've seen several reports where folks in the US have had shot out barrels rebored to a larger caliber and were very happy with the results.

338 Win Mag would work without any alterations. And you can still do the 375 H&H. You don't need another 30 cal; boring..
(As in, mundane and uninteresting)
I like the 358 Norma Mag. Even the 350 Rem mag is very capable and interesting.
I always rebarrel; I never rebore anything.

quote:

Originally posted by dpcd:
The answer is Yes, but...
The mag box is 3.4 inches, so you will need another one to accommodate a 3.6 round. No problem there,
Mill out the receiver a bit.
However you will have to make a new bolt stop because the original is very thin and will not allow modification for longer bolt throw. Not a complicated piece though; easily made on your mill. Go for it. Post pictures.
But since I got to know the 376 Steyr, I just use those now.
Oh, you want a 300; not a 375. Just go with the Win Mag.

Is there anyone making the 3.6” mag box?

Sure; Remington, Winchester; you; mag boxes are just pieces of sheet metal bent in the shape of a box. Nothing magic about them.
Or take the one you have and solder an extension onto it. Bring it over and we will do it.

As I understand it, it's a paperwork nightmare to rebarrel a rifle in RSA to a different caliber. You say the 7mm Mag won't shoot? Try setting it back a bit and recutting the chamber properly. And maybe the crown while you are at it. That may cure the problem.

There was a time when Ruger barrels were dubious though. If your barrel is a POS, I would go with a 416 Taylor. Should be just a barrel swap, maybe a tad off the feed ramp to widen it. You would have to reload of course. Brass is very easy, any short belted mag (incl the 7mm Mag) will do. You may struggle to find a reamer though. Hint, I have one, willing to trade for a baboon or warthog.