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TAKE ME TO SCHOOL ............??????

Discussion in 'Uncategorized Threads' started by Blakester, Jul 22, 2008.

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  1. Blakester

    Blakester TS Member

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    I would like someone to explain what it means for a Barrel to be .740 or .750 or .720 and which one is your preferance and why ..... ??????
     
  2. mixer

    mixer Well-Known Member

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    Those numbers designate the bore diameter. A standard 12ga bore is about .725-.729. I'll leave it to others to explain the reasons for larger bore diameters.


    Eric
     
  3. ec90t

    ec90t Guest

    Old school 12 ga barrels are .720 to .730". Newer generation barrels are .735 or better. Most of your better patterning guns will have backbores .740 or better.

    ec90t
     
  4. pendennis

    pendennis Well-Known Member

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    The standard bore on a 12 gauge is about .729. Anything larger is considered to be "back-bored". Back-boring reduces recoil, reduces shotcup friction, and improves shot patterns.

    Most guns, depending on the maker, will vary in their optimum performance. A Browning may perform better at .735, whereas a Kolar may do better at .750.

    It also provides for an endless number of arguments among shotgunners; like the #7.5 or #8 shot argument. There is probably a better chance of agreement among everyone as to the number of angels who will fit on the head of a pin, before you can get two trapshooters to agree on the amount of back-boring.

    Best,
    Dennis
     
  5. Blakester

    Blakester TS Member

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    I saw a new Kolar on GunBroker with a semi lite .750 barrel and didn't really know what that meant, I would have thought you would have wanted it smaller for a tighter pattern but I guess we are talking the back end of the barrel instead of the muzzel end where it is choked down...... Thanks Guys ; Ricky
     
  6. Bruce Specht

    Bruce Specht Well-Known Member

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    Where is the measurement of bore diameter made? at the action end? The other end would differ based on choke on a fixed choke gun???
     
  7. mixer

    mixer Well-Known Member

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    "Where is the measurement of bore diameter made? at the action end? The other end would differ based on choke on a fixed choke gun???"


    Measurement is made all along the bore until the reading gets smaller at the choke area. The difference between the two readings is the amount of choke. i.e. My Browning Broadway top barrel has a .725 bore with a choke of .695, .30 constriction which equals a full choke and patterning tests confirm it. Bottom barrel is .725 bore with .701 choke, .24 constriction for an improved mod choke. These are factory fixed chokes.

    Eric
     
  8. Bruce Specht

    Bruce Specht Well-Known Member

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    That was my thought but I needed to verify that I was correct.
     
  9. omgb

    omgb Well-Known Member

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    There is an ideal bore diameter to shot column length ratio for each gauge. With 16 GA for example, the reason why the 1 oz load is considered ideal is that at that weight, the length of the coloumn compared to the width of the colum in relationship to the standard 16 GA bore diameter, produces near perfect pattern densities at upland game ranges; 25-40 yards. Theoretically, the same is true for all gauges. Applied to the 12 gauge with 11/8 oz loads of number 8 and you get some of those odd bore diameters you mentioned earlier. As to which is best? Well, there seems to be some difference of opinion on that matter as you can see. That's my take on it anyway.
     
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