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Thread: Any mods available for 300wby to extend magazine box length for greater COL?

  1. #1
    Join Date
    Feb 2019
    Location
    Kamloops
    Posts
    4

    Lightbulb Any mods available for 300wby to extend magazine box length for greater COL?

    Just recently discovered this site and love how informative it is. I haven't had time to go through all the posts so not sure if this topic has been discussed already but does anyone know of or have any experience with extending the magazine box on a 300 Wby to achieve a greater cartridge overall length to seat the bullet closer to the rifling? Apparently it's possible with the 7mm so not sure why the .300 couldn't be?

  2. #2
    Join Date
    Oct 2011
    Location
    afognak island AK
    Posts
    441

    Default Re: Any mods available for 300wby to extend magazine box length for greater COL?

    Welcome aboard. 3.8" is the max coal for the MKV action if you want to load from the magazine. I am not positive but do believe the 300 has the longer magazine. Also when installing the longer magazine in say a 7mm, the bolt stop channel on the bottom of the bolt has to be milled longer to alow the bolt to travel reward enough to pick up rounds from the magazine.

    Hope this makes sense.
    Rob
    Education is expensive, be it university or emergency room

  3. Default Re: Any mods available for 300wby to extend magazine box length for greater COL?

    Hi, since the 300 Wby has the longer magazine it's the max length for the action. Seating the bullet farther out has little or no benefits since the freebore is a lot longer than max length. The freebore was made so Weatherby could use a heavier load with the powders available in the 40 and 50's. Today it's a different world concerning powders. I have tried to seat bullets farther out in different Wby calibers, but it seems not to improve accuracy at least in my rifles.



    Cartridge
    Throat length (free bore)
    224 Weatherby Magnum .162
    240 Weatherby Magnum .169
    257 Weatherby Magnum .378
    6.5-300 Weatherby Magnum .2037
    270 Weatherby Magnum .378
    7MM Weatherby Magnum .378
    300 Weatherby Magnum .361
    340 Weatherby Magnum .373
    375 Weatherby Magnum .373
    378 Weatherby Magnum .756
    416 Weatherby Magnum .239
    460 Weatherby Magnum .756
    30-378 Weatherby Magnum .361
    338-378 Weatherby Magnum .361

    RUM = Poor Man's Weatherby!

  4. #4
    Join Date
    Feb 2019
    Location
    Kamloops
    Posts
    4

    Default Re: Any mods available for 300wby to extend magazine box length for greater COL?

    Appreciate the responses. Needless to say I'm a little disappointed. I was really hoping to be able to achieve somewhere around a 4" COAL which would put me within .040" of the rifling with the 212gr ELDX bullets. Not to mention the loaded rounds would look pretty cool at that length!

    .340 Weatherby you mentioned trying to seat bullets out farther with several different calibers, I'm curious how close to the rifling did you get? Do you think having that much free-bore is unnecessary enough that you would suggest re-barreling and eliminating most of it? If for no other reason than to shave some weight from the rifle? My ultimate goal with this gun is a long range hunting/pack rifle.

  5. Default Re: Any mods available for 300wby to extend magazine box length for greater COL?

    Why disappointed? The long freebore has no negative input on your rifle. The truth is that most handloaders think that seating the bullets closer to the rifling improves accuracy. The truth in most cases is that you remove a lot of not so good reloading habits by doing so. Here is what you gain from seating the bullet closer/into to the rifling:


    • Bullets not in line with the throat/rifling will have a shorter jump or even be forced into the throat aligning the bullet with the bore.
    • The MV will be more uniform since the bullet is closer to the rifling even if the power charge is not uniform, or wrong powder giving erratic pressure.


    Look at Weatherby caliber's, they claim SUB MOA in their calibers with Weatherby factory ammunition.
    In my Weatherby's I have no problem shooting SUB MOA all day long.
    So, don't worry about not seating the bullets into the rifling, If you tune your reloads it still will shoot SUB MOA!

    RUM = Poor Man's Weatherby!

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