COL variance

Discussion in 'Reloading and ammunition' started by Larry, Jan 1, 2020.

  1. Larry

    Larry New Member

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    I try to be as close to measurements as possible and one thing that's always bothers me is that no matter how hard I try the overall length is always off by about 5 thousands. For the life of me I can't think what would cause the variance! I Would think the only possibilities could be press, case holder, dies, or xxx.
    Opinions please.
     
  2. Ratdog68

    Ratdog68 LSB Official Story Teller LoneStarBoars Supporter

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    I'd surmise it's in the overall length of the bullet. You're seating off the ogive to obtain the correct seating depth into the case, this is where your consistency matters (pressures). I'll bet that the variations you're finding are the distance from ogive to tip (manufacturing variable out of your control).
     
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  3. Larry

    Larry New Member

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    Thanks Ratdog. I understand what your saying but it's not the problem I'm trying to describe. I'm really not sure their is an answer. a thousandth of an inch is so small I think it may just be a problem caused by not properly cleaning press and case holder, or a worn press.

    If I'm re-loading 20 cases with 20 bullets and the base of my press is fixed and with a shell holder and the bullet seating die is fixed to a certain depth then the overall length of the cartridge (theoretically) should be the same for all 20 cartridges. Mine are varying from 2.238 to 2.244

    I hit on a possibility while I was typing - Hornady V-Max plastic tip may be moving during seating... Gotta do some more measuring but your thoughts would be appreciated...
     
  4. bar-d

    bar-d Head Wrangler, Chief Manure Manager: Bar-D Cattle

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    I agree with Ratdog. If you are measuring COAL to the tip of the bullet there will usually be some variation in the overall length of the bullet due to manufacturing variables as he said and also the size and construction of ballistic tips found in many bullets. If I am loading for as much precision as I can get, I use a Hornady OAL gauge and bullet comparator to set the length as measured to the ogive of the bullet. Sometimes mag length limitations dictate maximum COAL as in most AR magazines. For those, I get them to a happy medium that will consistently function in the mag and let 'em rip. I have not experienced much accuracy depletion for rounds that are within that "close enough for gubmint work" setting.
     
  5. Larry

    Larry New Member

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    HaHa yea, good stuff. I ain't doin no gubmint work since dey let me ouda the pen... lol
    Thanks and good hunting in 2020!
     
  6. Chopperdrvr

    Chopperdrvr Deep East Tx SUS VENATOR CLUB

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    If your bullet seating stem is designed to contact the bullet somewhere between the point of the bullet and the ogive, the variations in the bullet nose is what is causing that range. The only way to keep OAL exact, would be to have a seating stem with a flat contact surface, but that isn't as desirable.
     
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