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Rechamber 300 Wby?
Ray B
Member Posts: 11,822
I have a 300 Wby Mag barrel that I am considering having fitted to an Oberndorf '98 action. the action is large ring/ large thread so the barrel would screw right in, but the action would need to have the magazine lengthened and the lower lug ramp moved forward, which I'm reluctant to do. so an option would be to take a thread or two off of the barrel and rechamber for a shorter cartridge. If Weatherby made a 300 similar to the 257/270/7mm case, that would be the obvious choice- but since they don't I'd have to get custom made dies, which I'd prefer to avoid. So of the cartridges that fit the bill as standard action/30 caliber/magnum, I'm leaning toward the 30/338. I prefer it to the standard 300 Win Mag. Other than opening the boltface, there should be minimal action changes- I think. am I correct??
Comments
http://en.wikipedia.org/wiki/.308_Norma_Magnum
My .30/.338 is built on a 1903/A3 action and feeds fine. Of course that magazine will accept a C.O.L. of 3.34".
By the time you shorten the chamber end of the barrel enough to rechamber it for a shorter belted magnum, to be able to clean up the old 300 WBY chamber, you might not have enough meat in the chamber area. Something to look into.
However, you might have enough to chamber something like the 300 WSM, or 300 RSAUM. You will have to adjust the feed ramp, action rails, and magazine follower, for anything you rechamber to, but would not have to adjust the magazine length.
Best
EDIT 1
quote:unless one of the 404 based cases was used.?
Those full length 404 cases would not fix your magazine length problem...your sole reason for wanting to rechamber to a shorter magnum to start with.
The WBY is 0.492 at the shoulder, as a distance of 2.298 from the head face. A regular 300 Win(Belted) is 0.489 at the shoulder, at a distance of 2.196...all on inches. All meaning you will have to go deeper yet to totally clean up the WBY chamber. With anything you do, you will have to clean up the minor case neck to shoulder radius too. Since you are going that deep, if you go with the WSM or RSAUM, you can clean up the whole WBY chamber, and still have enough meat left, and magazine room...the latter being the reason you are rechambering in the first place.
Best
Ray B,
By the time you shorten the chamber end of the barrel enough to rechamber it for a shorter belted magnum, to be able to clean up the old 300 WBY chamber, you might not have enough meat in the chamber area. Something to look into.
However, you might have enough to chamber something like the 300 WSM, or 300 RSAUM. You will have to adjust the feed ramp, action rails, and magazine follower, for anything you rechamber to, but would not have to adjust the magazine length.
Best
I'm a little confused on this- it seems to me that the shoulder of the 30/338 would only need to be far enough forward to absorb the double radius Wby shoulder. I'm guessing that the reason to go farther forward would be if the body diameter of the Wby was larger than the 338 then virtually the entire chamber would need to be removed, unless one of the 404 based cases was used.?
.300 Weatherby Magnum
.338 Winchester Magnum
All you need to do is some simple subtraction to figure whether or not this is possible. Given that the M98 Mauser thread tenon is only about 0.625" or so long and you need to shorten the chamber by 0.325" just to make the shorter cartridge you ask about, you have lost 1/2 of the thread tenon right from the get go. It's not just a 'thread or two'.
So now you have to create a new tenon length and thread it if you find that the original chamber features will clean up using the new, shorter chamber reamer. This includes the WBY neck and shoulder of course, so check the dimensions carefully. If they don't clean up then you need to remove more of the tenon, all of it most likely.
Then you need to determine if there is enough straight line shank on the barrel left in order to create the new tenon.
By the way, we've been modifying M98 Mauser actions to accept the H&H line of cartridges safely and reliably for quite a few decades now. So you might consider leaving the chamber alone, fit and adjust the headspace and buy some new or modified bottom metal. Otherwise a different barrel might be more appropriate.
Best.
That's what I wrote above in the first two paragraphs. Good news is that you have extra tenon length and diameter sufficient to complete the new chamber correctly.
Good Luck! We'd be interested in a field test when you get it back from the gunsmith.
Best.