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Odd Vertical Stringing

Rocketmandb

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Minuteman
  • Nov 2, 2018
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    I went out to the hills today with a couple friends and we were shooting a variety of rifles at 1600 and 2200.

    The odd thing was the vertical stringing we were getting with my 37XC. All three of us experienced it. I was chono-ing every shot, and we'd see a few shots either hit or go slightly to one side (wind was a factor), then the next go way high or way low - like a mil+ high or low. Velocity was very similar between the shots. When we checked the target at the end of the day, we found a number of nearly intact bullets. The interesting thing was that we found a few that had packed dirt on the back side of the bullet, indicating that the bullet impacted the dirt ass end first. Either they ricocheted and impacted back in, or they were tumbling, which I find to be unlikely, considering the bullets should not go subsonic until about 2800 yards. Bullets were Lehigh 353s, muzzle velocity was roughly 3035 - 3045 fps., DA 2400', temp 55, wind at roughly 5:00, 8-12 mph and gusty.

    Pic of the recovered bullets:
    IMG_0439 copy.jpg


    I'm interested in the ring around the near center of all the bullets (approximately where the neck terminates on seating). Closer in (up to ~a mile), this rifle with this bullet does pretty well. Farther out, things start to fall apart.

    On a side note, all the rain we're getting in Cali is making the hills come alive with wild flowers - shooting in this environment right now is surreal.

    IMG_0433 copy.jpg
     
    Those bullets look normal to me.
    And if you back your seating die up a full turn then lower the seating stem to achieve the same seating depth you won't see the case neck digging into the bullet
     
    Those bullets look normal to me.
    And if you back your seating die up a full turn then lower the seating stem to achieve the same seating depth you won't see the case neck digging into the bullet

    Could you explain why that occurs? The point will be moot anyway as I'm ordering an arbor press die from Warner, but I'm interested to know regardless.
     
    Normally one would put a piece of brass in the shellholder and run the presses ram all the way up.
    The seating die would then be screwed down until it makes contact with the brass and then backed off a full turn or 2 turns.
    The seating stem would then be used to adjust the seating depth to the desired length and all is well.
    If you adjust the die down to set the seating depths length you run the risk of running the cases mouth into the die and digging into the bullet like a pistol die would be setup.
     
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    @cameljockey230 - thanks for the info. I reset the die after I got back from travel, then loaded a dummy round and pulled the bullet. I'm not seeing any ring, so I'm hopeful that when I go back out next week, I don't see the problem.
     
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    I had an issue like this with a 300 PRC last summer. ES’s were sub 15, but I had vertical stringing +/- a mil and occasional random flyers shooting 230 A-tips from 800-2k.

    Ended up being a brass issue where I didn’t check case length after a couple firings and they were long in the tooth. I’m guessing when the rounds were chambered there would occasionally be a case long enough to dig the case mouth into the bullet and damage it enough to see the BC variation I was experiencing.

    A trim to min length and reset of the neck chamfer seemed to fix things for me, hopefully your issue resolves similarly.
     
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