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12 ga. Back boreing

Discussion in 'Shooting Related Threads' started by bakergun, Nov 20, 2009.

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  1. bakergun

    bakergun TS Member

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    Can some one please tell me what is the maximum you can back bore a 12 GA, barrel ? I have heard .740 max. so you won't loose velocity. I have a chance to get a .743 back bore will this loose velocity. Its choked .040 any help would be appreciated.
    Pete
     
  2. Trap2

    Trap2 Well-Known Member

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    Pete...
    My DB-81 single barrel is back bored to .742" by Tom Wilkinson and it is fantastic. Stan Baker used to go as far as .800" in some barrels, which became known as "Baker Big Bores". Your .743" barrel will do everything you want it to do without losing any velocity. It should not be a problem.. Dan Thome (Trap2)
     
  3. PerazziBigBore

    PerazziBigBore TS Member

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    My Seitz is a .752.. Flawless
     
  4. W.P.T.

    W.P.T. TS Member

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    Not sure on a standard bore but Baker was making back bored barrels with .750 bores and they worked fine ... Thats a lot of choke in any gun with todays ammo but if it works for you thats great ... I would check with some of the gunsmiths and see what they tell you, it would be interesting to hear what they have to say ... Keep us posted ... WPT ... (YAC) ...
     
  5. bakergun

    bakergun TS Member

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    Can you please tell me what the 0.40 represents .I thought it was the size of the choke but when I use micrometer 0.40 would be a 410 ga mod
     
  6. jhoward

    jhoward Member

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    The .40 is the constriction of the choke, not the bore diameter. So if bore diameter is .743 with a .40 choke then the muzzle diameter should be .703. A standard 'full' choke is ~.30 constriction.
     
  7. bakergun

    bakergun TS Member

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    jhoward
    Thank you for exsplaining that
    Pete
     
  8. skeet_man

    skeet_man Well-Known Member

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    My kolar is .750, and I haven't met a shell yet that my gun couldn't digest except some one oz loads w/ international clays, but i'm pretty sure those wouldn't have worked in any gun due to the component combination I had chosen.
     
  9. Gregg535

    Gregg535 Member

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    Bakergun,

    Jhoward has probably just made a mistake in the way he is expressing that choke measurement --- it needs to be expressed as 0.040 and not as 0.40. It represents that actual measurement. That 0.040 is the amount of constriction provided by the choke; in other words, the tightest inside diameter area in the choke is 0.040 less than the barrels internal bore size.

    As far as what is the maximum size that a 12 gauge barrel can be safely backbored, there is no single number to answer that question as shotguns barrels from different manufactures will vary by quite a large amount in their size ---- both with the outside dimension and the inside bore size. Some barrels are quite thickly walled and can have a lot of metal removed but some are quite thin walled to begin with and don't have much metal to play with. Also, some gunsmiths/barrelsmiths have somewhat different ideas of what amount of metal can be safely removed as far as backboring and also for lengthening forcing cones.
     
  10. jhoward

    jhoward Member

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    Yeah, looks like a left out a decimal place. .40 would be a hell of a tight choke. :p
     
  11. ramorton

    ramorton TS Supporters TS Supporters

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    I shoot a .035 choke thru the .750 i.d. Kolar MaxTa. No recoil and could not tell any difference in velocity with 2/3/4 shells. Shoots the same with 3 dram. Crushes targets. What I like is the balance of the Kolar Max Ta. The high rib and the head's up position. I shoot only factory loads. Roy
     
  12. PerazziBigBore

    PerazziBigBore TS Member

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    Kolar going to the .750 bore was the best thing they ever did for dynamics.. It made their gun very responsive.. It took that to get my vote.. I've always loved their design.. but found the earlier ones heavy..and slugish.. the .740 bore was good.. but the .750 has my vote.. They also pattern quite well.. right out the box..
     
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