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Backboring Kolar .740 bore barrels?

Discussion in 'Uncategorized Threads' started by skeet_man, Jun 17, 2007.

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  1. skeet_man

    skeet_man Well-Known Member

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    has anyone out there had a set of .740 bore Kolar barrels w/ screw chokes backbored? Mine actually measure .737 and .738. I need to loose 2-3oz from these barrels to get them to match in both weight and balance the barrels I use for my subgauge tubes, and figure if I had them taken out to .745 or maybe .750 (i'd figure out the exact amt of weight i need to loose, then tell whoever does it to backbore it to that weight regardless of ID), it'd get the weight and balance where I want it. My only worry is being able to use the choke tube threads w/ out having to have them re-worked. Are the .750 and .740 bore kolar chokes the same except for ID (same thread and OD)? Any recommedations on the work? I'm thinking Allems or Wrights.
     
  2. ramorton

    ramorton TS Supporters TS Supporters

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    Send your barrels back to Kolar. Let them take them out to .745 or .750. You will only have to open the chokes, this will be expensive. Why don't you trade the barrels for .750 barrels?Hope this helps, Roy
     
  3. skeet_man

    skeet_man Well-Known Member

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    roy- would love to be able to trade them for .750 barrels if something comes along (what I have are .740 bore flat taper rib barrels, could cut alot of work and headache out if I could trade them for .750 bore step taper rib barrels killing about 3 projects w/ one stone), that will save alot of work. Getting new chokes won't be a problem, just want to make sure my choke threads would be compatiable with a .745 bore or .750 bore choke tube (don't know if the choke walls would be too thin).
     
  4. claybrdr

    claybrdr Well-Known Member

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    Choke tube threads would NOT be compatible.
     
  5. ramorton

    ramorton TS Supporters TS Supporters

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    Why don't you call Tom Wilkinson, he is an expert on this type thing since he is now installing choke tubes with backbored barrels.He has done an amount of work for me that has been first class and is very knowledgable regarding barrel I.D. and O.D. Wall thickness will play a part in this work. You will have to caliper all your chokes and I.D. before you take on this project. Remember, you will need to have enough wall thickness left to insure safety. I do not know if Kolar has the same barrel O.D. on .740 and .750, that will make a difference. Good Luck, Roy Tom's # is 919-603-0167
     
  6. Neil Winston

    Neil Winston Well-Known Member

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    Let's work this out.

    Steel has a density of about 0.285 lb/cu in.

    So a rod of steel of 0.75 inches has an area of 0.375 squared times pi or 0.442 sq, inches and if it is 34 inches line has a volume of 15.0 cu. in and weighs that times 0.285 or 4.28 pounds.

    Doing the same calculations with a 0.740 rod we get 4.16 pounds.

    That means that a difference of 0.05 inches equals 0.12 pounds or 1.9 ounces.

    I think that means it could be done, weight-wise at least.

    Neil
     
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