Switchbarrels and barrel bedding pads

Discussion in 'Gunsmithing' started by duster, Mar 28, 2008.

  1. duster

    duster Member

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    May 20, 2007
    I have a switchbarrel rifle built on a custom benchrest action (P.A.S.). The action is quite long (9-1/4") and has a magazine cut out. The barrels are a 28" 30-378 and a 32" 338 Lapua Imp. Both are heavy contour barrels having muzzle diameters of .860" and .930" and major diameters of 1.238" and 1.250" respectively.
    I am trying to decide on the need to use a barrel pad when I bed the action in the McMillan stock. The barrel pad can only be correct for the larger of the barrels.
    Is a barrel pad an essential ingredient in bedding a precision long range repeating rifle? Does the pad contribute to vertical dispersion as the barrel heats such as in 1000 yard competition? Or does it reduce vertical dispersion in general?
    I suppose I could bed the larger barrel with a pad and let the lighter barrel free float.
    I am skeptical whether the barrel diameters could be made exact so that one bedding pad would fit all. In any event I seek a simpler solution.
    Would like to hear from anyone having having a suggestion on how to handle this especially those experienced with this aspect of switchbarrel benchrest rifles.
    Thanks
     
  2. James Jones

    James Jones Well-Known Member

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    What is the diameter of the action (not framiliar with P.A.S.). The Rem 700 is said to be fine supporting a 30" #8 conture barrel but it depends on who you ask.

    I would think if the action is at least 1.35" like the rem or bigger and the tennon is at least 1" it would be fine.

    I knew a fell one time that had a swithch barrel gun from a #5 conture to a full bull and he liked having the first 6" bedded , he made an adjustable bedding pad that he adjusted with a torque wrench for each barrel. I can't say that it worked 100% but both barrels shot well , I though if nothing else it was an intresting idea.
     

  3. DandT

    DandT Member

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    I build 20-25 rifles a year in the calibers you mentioned as well as many other stitch barrel guns and calibers and I personally prefer to pillar and epoxy bed the action but allow the barrel to be fully free-floated. This offers the greatest accuracy advantage as there is no barrel contct with anything that can cause unnecessary vibrations which can change the harmonics of the barrel to possibly be different from shot to shot and have an advers affect on accuracy at extreme ranges....

    D&T
     
  4. Lightvarmint

    Lightvarmint Guest

    Depending on your action diameter, you should be fine without a barrel pad. I have some barrels that are 32" (with muzzle brake) and 1.2" without any taper on my 1.5" actions. However, contact Shawn Carlock (advertiser here on the website) and ask him. I am sure he will steer you in the correct direction.

    James

    James
     
  5. duster

    duster Member

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    The action is 1.420" diameter. The tennon is approx 1.2" and there is approx.1.4" of action length ahead of the front action screw.
     
  6. NesikaChad

    NesikaChad Well-Known Member

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    Suggestion:

    Search/read my threads/posts regarding pillar bedding. Experience has shown me that if you follow this procedure you can run with the heavy sticks and not have to run a barrel pad.

    Short of cylindrical grinding on centers, you'll never fit those two barrels to where you can be reasonably confident you are not binding things up in the stock.

    I've built LOTS of bolt guns without anything other than the action touching the barrel and they all shot exceptionally well.

    Good luck.

    Chad
     
  7. duster

    duster Member

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    Many thanks to all who took time to respond to my question. I will bed without a barrel pad.