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What's the unit of measure in an 18.7 choke tube?

Discussion in 'Shooting Related Threads' started by flyfish, Jun 26, 2012.

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  1. flyfish

    flyfish Member

    Jan 29, 1998

    Perazzi makes an 18.7 choke tube series. 18.7 what? What's the unit of measure. Thanks in advance.
  2. cunninmp

    cunninmp Member

    Nov 15, 2008
    Two is dead on the money. Bore size is .736.

    Mike C.
  3. WoodsonEnt

    WoodsonEnt Active Member

    May 20, 2008
    Easy conversion of metric system: MM to English Inch is 25.4

    18.7 / 25.4 = 0.73622047244 (.736 bore)

    Same applies for rifle bullet diameter....6mm / 25.4 = .236

    Multiply inch to convert to metric.... .308 x 25.4 = 7.8232mm
  4. MDMike

    MDMike Well-Known Member

    Nov 30, 2011
    As others have said here, 18.7 mm is the bore size. It should also be the measurement at the begining or back end of the choke tube. So an 18.7 choke tube with a .027 constriction (full I believe), would be 0.708, or the front or end of the choke tube where the shot and wad exits. (0.736 - 0.027 = 0.708)
    Now converting this back into metric, a full choke tube would measure 18.7mm on the bore end, or where the shot and wad enters the choke, and 17.98 mm at the constriction, or where the shot and wad exits the tube.
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