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Bullet size question

Discussion in 'Handloading and Reloading' started by Eric F, Feb 6, 2008.

  1. Eric F

    Eric F Well-Known Member

    ok say I slug my barrel and the bore is .xxx and the groove depth is .xxx+.010 If I were to shoot jacketed bullets what size do I go with and if I shot lead what sixe could I go up to?
  2. rcmodel

    rcmodel Member in memoriam

    For jacketed bullets use the measured slug dia..
    So, a .308" slug measurement would need .308" jacketed bullets.

    For lead rifle bullets go actual slug dia, or slug dia. + .001"

    For lead bullets in revolvers, measure cylinder throat dia, and if they are bigger then the slug measurement, ignore the actual barrel dia.

    The reason for this is many older revolvers had very over-size chamber throats. You want the bullet to fit the throat when it comes out of the case, and then it will slug down to fit the bore if necessary.

    When you measure the lead slug O.D., you are measuring the actual groove diameter of the barrel. The actual bore dia is at the bottom of the grooves on the slug, and are very difficult to measure.

    Just measure the outside of the slug on the high points of opposing rifling marks, and do not add .010" to it.

    You can never assume all rifling grooves are going to be .005" deep because very few of them are. For instance, most conventional rifled .308 barrels have a .300" hole drilled & reamed through it, and the rifling grooves are then cut .004" deep.

  3. rcmodel

    rcmodel Member in memoriam

    Dup post!
    Last edited: Feb 6, 2008
  4. rcmodel

    rcmodel Member in memoriam

    Dup post!
    Last edited: Feb 6, 2008
  5. ranger335v

    ranger335v Well-Known Member

    Use the .xxx + .010 for both at first. You want the bullets to fit the bore.

    Some - many - factory bores are as much as .001 oversize so it is good to size cast bullets that much over for them but it is only to make the bullets fit those bores. Another factor is the effect of seating a soft lead bullet in a tight case neck, the neck can actually reduce the diameter of the bullet as much as a thousant so it can be good to start that much oversize. But, in either instance, it's not consistant for all guns so try the fit of a bore size lead bullet as well as oversized.

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