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Thread: acceptable seating depth variations

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    Default acceptable seating depth variations

    What is your allowable seating depth variations for Hunting rounds. I am shooting a 300 win mag. these days with 180gr Barnes TTSX.

    I try to be .001 +/-. I throw some rounds out and tinker a bit with the die.

    It takes a while to load a bunch of rounds. I would like to speed up the process a bit.

    Also, I think the Tipped TSX bullets are different lengths occasionally. There is a small space under the plastic tip on some of them. I have not measured this though. I am looking more closely now at each bullet. This will obviously mess with the COL. The bullet should hit the lands the same though I would guess.

  2. #2

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    Daved .....

    For my hunting rifles, I like to start with the longest OAL that will fit in the magazine. Then I experiment with "shorter" OAL loads to see if accuracy improves. (Sometimes it will improve.) That way I can always use the magazine. I take measurements on the bullet ogive to get consistent readings from varying bullet tips.

    For my long range rifles (with no magazine), I start with the loads about -.001" behind the rifling. Again, I shorten the OAL in .003" increments and shoot groups to find the most accurate load.

    I also like to have -.001" to -.002" chamber clearance (at the case shoulder), and I use the same tool to get all of these measurements. Check it out on my website. WWW.LARRYWILLIS.COM

    - Innovative

  3. #3
    Member marshall's Avatar
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    Quote Originally Posted by Daved View Post
    What is your allowable seating depth variations for Hunting rounds. I am shooting a 300 win mag. these days with 180gr Barnes TTSX.

    I try to be .001 +/-. I throw some rounds out and tinker a bit with the die.

    It takes a while to load a bunch of rounds. I would like to speed up the process a bit.

    Also, I think the Tipped TSX bullets are different lengths occasionally. There is a small space under the plastic tip on some of them. I have not measured this though. I am looking more closely now at each bullet. This will obviously mess with the COL. The bullet should hit the lands the same though I would guess.
    If you seat each bullet and use the ogive as a reference you will find that COL varies. The COL variance isn't a big deal as long as it fits in your magazine.

    The consistent accuracy comes from distance established off the lands and that's measured at the ogive. If your bullets are all different lengths then they are different weights too. That will cause accuracy issues down range.

    I've found Barnes to be +/- .8gr in the same box, that's quite poor when compared with Sierra Match King or Berger VLD which are generally +/- .1gr. I sort them into groups of equal weight in find that they are closer in length. Once seated with an ogive measurement the COL is very close, generally +/- .002 I found that max magazine length minus about .015 worked the best in my example. The throat was too deep to get the bullet COL long enough to approach Barnes .050 off the lands recommendation. When hunting I don't think it's advisable to make the cartridge so long that it won't feed from the magazine.

    I worked with Barnes TTSX, TSX and MRX in a 300RUM. We shot well over 50 rounds of each bullet type playing with charges and seating depths. The standard TSX out performed it's more expensive brothers. The MRX was the worst and most expensive in our testing.

  4. #4
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    As marshall said, the length to the ogive is truly what matters, as it is the distance from the lands and grooves. I was pulling my hair out on some Nosler Custom Competitions because I couldn't get consistent with OAL within .004". I actually bought 2 more sets of dies, thinking the seating dies were pieces of crap. I finally got a Hornady comparator set, and low and behold, they all had consistent ogive depths to the nearest .001". This makes sense, since the seating die doesn't push on the tip, it pushes farther down. As long as the ogive seating depths are the same, I've noticed no accuracy differences. Which, by the way, my Kimber hates Nosler bullets, and I wasted my time anyway... Only Barnes TTSX's are good enough for my stuck up rifle.

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