seating depth increments?

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by rufous, Feb 23, 2004.

  1. rufous

    rufous Well-Known Member

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    My gunsmith suggested that my 6-284 would most likely shoot best with the Sierra 107 matchking bullet seated 0.010” to 0.015” into the lands. I plan to go out and try several different seating depths and wonder what increment to use? Should I try just touching the lands, 0.005”, 0.010” and 0.015” into the lands or should I try in 0.001” or 0.002” increments or what? Thanks, Rufous.
     
  2. sniper2

    sniper2 Well-Known Member

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    I start touching the lands,usually this will work if not drop back two thousands and so on. There will be a sweet spot some where!
     

  3. BountyHunter

    BountyHunter Writers Guild

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    I like to test for serious load development at 300-400 yds under no wind conditions early in morning or evening, firing several groups to confirm what I think is serious load.

    BH
     
  4. Varmint Hunter

    Varmint Hunter Well-Known Member

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    I don't believe in seating bullets to "just touching the rifling", particularely with production bullets.
    First of all, production bullets (and customs to a lesser extent)can only be produced within certain tolerances. Base to ojive distance varies, curvature of ojive varies, bullet length varies and on and on.

    Additionally, it is difficult to get an EXACT measurement of your chamber/throat with the current maesuring tools. If you are within 1-2 thousandths than thats pretty good, but you also have to remember that the throat is always receeding slightly too. It doesn't take much for a throat to erode .001".

    Given the inevitable variences of a few thousandths, if you try to "just touch the rifling" than one round may do just that while another is .001" into the rifling and another is .001" off the rifling. That is three very different conditions, and all within .002" of variation from bullet base to bearing surface of the bullet.

    I much rather work .005"-.010" into or off-of the rifling. This way a variation of a few thousandths will not cause a significant change in engagement.

    Sako7STW,
    Provided that the wind is favorable, group size changes are normally more evident as range increases.

    Just my thoughts - VH

    [ 02-27-2004: Message edited by: Varmint Hunter ]
     
  5. Rokchukrslave

    Rokchukrslave Member

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    I agree with VH. You cannot hold those kinds of tolerances to be "just touching the lands". Some will be just touching and some will not.
    I seat my Berger VLD's in .308 .015 into the lands.
    If you want to seat into the lands, I would start at .010 into the lands and then proceed with increments of .005.
    I say to start with them .010 in so that with your possible tolerance stack, you will still have all bullets touching the lands for sure.
    My .02
     
  6. Sako7STW

    Sako7STW Well-Known Member

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    At what distance would you be best able to see the effects of the seating depths? 100, 200, 300....?
     
  7. HoytemanPA

    HoytemanPA Well-Known Member

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    This may be a dumb question but can't you get and or customize a bullet seater to contact the bullet with the exact same taper and contact point as your lands? Or is it that the seater being full contact all the way around could differ since the rifling only contacts the amount of lands that you have? And if this is the case, that the bullet seater may touch a "high" spot around an imperfect bullet, would this not error on the safe side? Meaning if a seater were set up this way a bullet could never be seated too long?

    Just some questions,
    Thanks, HPA

    Alright I just reread again and I think I got it. The error on the safe side could be the cause of inaccuracy therefore either crammed in or away from the lands, gotcha.

    [ 03-01-2004: Message edited by: HoytemanPA ]