300RUM build with 210VLD COAL?

Discussion in 'Gunsmithing' started by Tumbleweed, Feb 21, 2010.

  1. Tumbleweed

    Tumbleweed Well-Known Member

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    Hello guys, could use a little input here. I have a Rem 700 in 300wby with a 27" #5 lilja on it. I use 210VLD's exclusively but want a little more speed. I have decided to rechamber to 300RUM. My question is in regards to COAL. I have an outstanding gunsmith who is very familiar with the 300RUM but has never set one up for 210VLDs. We talked about setting the rifle up initially for 3.600 as the standard COAL. This however puts the Berger very deep into the case possibly causing a loss of capacity. I am almost certain that the bullet will need to touch the rifling or be .010 off, that is what I was doing before to get accuracy. I am not concerned about fitting the cartridge down in the magazine, if it needs to be a single shot so be it. I will probably be able to put one down like before anyway. What are your recommendations and experiences with this set up, do we need to go longer COAL like 3.700 or so? Thanks, Jesse
     
  2. NesikaChad

    NesikaChad Well-Known Member

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    When building a rifle with the intention of ignoring the idea of it being functional/practical I let the bullet determine the seating depth and the chamber's throat/freebore-meaning I follow a simple process.

    Most have heard about the dreaded "doughnut" located at the neck/shoulder junction. This is reported to cause potential deviations in velocity due to inconsistent neck tension/release tension. The simple solution is to avoid it. Seat the bearing surface/boat tail junction just above the neck/shoulder junction and then throat the barrel accordingly. This will give you the case volume to get the load density you want.

    From there just bump your seating depths in either direction until the rifle settles down and starts plotting shots the way you want it. I'd advise having the reamer made based off the cartridge length, but it could be throated with a ream after being chambered also.

    Good luck.

    -C
     

  3. Tumbleweed

    Tumbleweed Well-Known Member

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    "I'd advise having the reamer made based off the cartridge length, but it could be throated with a ream after being chambered also."

    My gunsmith will cut the chamber and then we will ream the throat out depending on what COAL we decide to go with.
     
  4. cedarswamp1

    cedarswamp1 Active Member

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    In my 300 rum .007 off the lands gives me a OAL of 3.8"

    This puts the bearing surface/boat tail junction slightly below the neck/shoulder junction.

    Your mileage may vary.
     
  5. Tumbleweed

    Tumbleweed Well-Known Member

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    Cerdarswamp, what kind of velocity are you getting and what kind of accuracy? What is your load data?
     
  6. cedarswamp1

    cedarswamp1 Active Member

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    Sorry Tumbleweed, I've yet to dent a primer on these, just started working with the 210 VLD.