Weatherby mark v conversion

Discussion in 'Gunsmithing' started by BLC3128, Mar 15, 2019.

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  1. BLC3128

    BLC3128 Active Member

    Jul 1, 2017
    I have a mid 1980s Mark V Deluxe in 7mm WBY Magnum. Can I re-barrel it to a 340 WBY. I understand that the bolt face diameter is the same and I do know I will have to swap the magazine. I would like to put a slightly heavier barrel than the "whippy" barrel it has. So is this a possibility? Can someone please walk me through this process!

    Also, I do not need any suggestions to rebarrel to "something else" as if I cannot rebarrel to 340WBY I will simply get a new and heavier contour 7mm WBY barrel with a faster twist!

    Thanks in advance!

  2. Dr. Vette

    Dr. Vette Well-Known Member

    Dec 30, 2009
    You will need a new magazine, or remove the partition from yours.
    You will need a new longer follower.
    I would recommend a new magazine spring, though you don't "need" one. You will appreciate it, though.
    You will need to have the bolt stop slot on the bolt machined for the longer length of the 340.

    Weatherby will sell you all of these parts, but they're moving right now so give them a lot of leeway on time.

    Or you can buy the pretty 340 I have and be happy. :D
    BLC3128 likes this.
  3. just country

    just country Well-Known Member

    Aug 6, 2014
    morning, I own a 340 accu-mark. factory muzzle brake. warne
    steel rings and mounts. Nikon Monarch 6.5x20x44. 210gr.
    Barnes bullets, fed. 215, 4831sc. weatherby brass.
    the weapon is a hammer. very accurate. I use this load for
    every kind of meat collecting. I will never sell this
    weapon. very comfortable to shoot. justme gbot tum
    Laelkhunter likes this.
  4. jreagle

    jreagle Well-Known Member

    Jan 19, 2012
    you may consider giving the Weatherby Custom Shop a call. Great people to work with. They can take you through what needs to be done to get where you want to be.

    I had them convert a mkv 300 japan to a 7mmRM a couple of years ago. I sent them the barreled action, documented the condition upon receipt and they went to work; took +- 6 weeks. Removed the #2 contour 300 barrel and installed an accumark #3, included new mag box and follower for around $600 door to door. very happy with the experience.
    I bedded a new stock from Stockys that would accept the heavier barrel.
    I am running the 7mm loads long now (.010" off the lands) so the original 300 mag box and follower is back on to hold those rounds.
    BLC3128 likes this.
  5. J E Custom

    J E Custom Well-Known Member

    Jul 29, 2004
    Converting to the 340 is straight forward with only a few changes so yes.

    I also have found that a heavier barrel makes a huge difference in accuracy and recoil. Even then the 340 is powerful and recoil management is recommended. I have built many rifles using the Mark 5 action and it is one of my favorite actions.

    Often they have been for the ladies that want to Elk hint and with a good muzzle brake can have the recoil of a 308 and is an absolute hammer for Elk sized game. Surprisingly the ladies love the 340 when set up correctly.

    BLC3128 and Dosh like this.
  6. BLC3128

    BLC3128 Active Member

    Jul 1, 2017
    I appreciate the input!
  7. Laelkhunter

    Laelkhunter Well-Known Member

    Oct 20, 2011
    Call Rich Reilly at Hi Tech Custom Rifles in Colo Springs 719-667-1090. He worked wonders with my Mark 5 on a rebarrel and Cerokote. I would trust him as far as what it would take to rebarrel yours to a .340. The brake he installed on my .340 makes it a dream to shoot.