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Thread: Bullet comparator diameters

  1. #1

    Bullet comparator diameters

    What diameter are bullet comparators - do they match the groove or rifling? E.g. for a 243 are they 0.243" or 0.236" (6.17mm or 6mm)?
    "A man can never have too much red wine, too many books, or too much ammunition." -- Rudyard Kipling

  2. #2
    Established Poster
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    Harry, I use the Sinclair nut shaped comparator Sinclair says that the holes are reamed the same as your chamber and as near as I can meassure my 6mm hole is tapered from .240 to .236

  3. #3
    Thanks Robert - you mean it starts at .240 where the bullet sits?
    "A man can never have too much red wine, too many books, or too much ammunition." -- Rudyard Kipling

  4. #4
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    Yes the hole is tappered the same as the rifles leade, the earlier models hole was .240 straight

  5. #5
    Harry.
    Hornady measures out at;

    .22 .212
    .24 .230
    .30 .296

    They are all straight. hope this helps.

    Spiker

  6. #6
    Thanks guys. Sounds like they vary between makes then. Those Hornady ones are way under bore (rifling) diameter then...
    "A man can never have too much red wine, too many books, or too much ammunition." -- Rudyard Kipling

  7. #7
    Not only do they vary between makers, they vary within makers. The within-maker variations are relatively small, but not insignificant. Small variations in the diameter - as I'm sure you are aware or you wouldn't be inquiring - can result in large differences in cartridge overall length depending on the ogive of the bullet.

    If you are 'serious', you can cast or slug your throat/leade/neck area and have your index reamed to the exact land diameter. When I cut a new chamber, I use the reamer used to cut the chamber to set the diameter of my Comparator index. All of the Hornady indices I have measured are 'conservatively' dimensioned.

    Paul

  8. #8
    I guess so long as the curveture of all the bullet noses are the same, it doesn't matter what diameter they are... But that is a big ask and I doubt they are. Although if they are very close (which I'd say they would), the actual difference in length you're measuring will be very small indeed - like less than calipers could measure I would have thought? You know, sine rule etc..

    Basically I would have thought, so long as you use the same comparitor, and only using it for comparing to a reference (or a few) dummy round it'll be close enough even for match shooting, let alone hunting. But I guess it's even debatable you really need it for hunting at all.
    "A man can never have too much red wine, too many books, or too much ammunition." -- Rudyard Kipling

  9. #9
    But I guess it's even debatable you really need it for hunting at all.
    That depends both on your attitude about precision reloading and whether or not you subscribe to the premise that seating depth (or distance from the lands), is an important factor in precision reloading.

    I couldn't agree with you more that having the exact land diameter in your comparator is rendered moot for many uses as long as you stay to using one comparator. (Simply keeping things relative.) However, if you want to be a specific distance from your lands (manifested in a specific cartridge overall length), then knowing exactly - not relatively - where your lands are is imperative. Personally, I don't find it possible to be more consistent than about 0.003" in cartridge-to-cartridge lengths (ogive length). Given all of the other variables (between cases capacity variation for one big one), 0.003" is sufficiently precise for my 'mental health'.

    Paul

  10. #10
    Well Paul I can safely say I agree on all fronts. If I'm within 3 thou length for my hunting loads I'm pretty happy.
    "A man can never have too much red wine, too many books, or too much ammunition." -- Rudyard Kipling

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