Bullet Seating Depth

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    • #1835
      Al Barr
      Participant

      If you were breathless and spellbound on the subject of neck tension; then you are gonna love seating depth.

      1) VLD bullets like to “jam”

      2) Secant Ogive bullets like to “jump”

      3) What do hybrids like to do?

      4) What is your technique for determining “touch” or CBTO (combined overall length cartridge case base to ogive)?

      5) What is your opinion of the relationship of seating depth and “pressure”?

      6) What increments (example .002, .005, .010) do you use in search of the “perfect” seating depth?

      7) Last question: Do you determine seating depth before or after powder charge?

      Come on men, give me some help here.
      Al

    • #1839
      Tony Graham
      Participant

      3) What do hybrids like to do?
      Bryan Litz says to start at .015” jump with the Hybrids

      4) What is your technique for determining “touch” or CBTO (combined overall length cartridge case base to ogive)?
      1. Seat the desired bullet long.
      2. Chamber it.
      3. Eject it and look for square land marks.
      4. Seat the.005” deeper and remove the landmarks w/ steel wool.
      Repeat until the land marks disappear.

      5) What is your opinion of the relationship of seating depth and “pressure”?
      Into the lands=higher pressure.

      6) What increments (example .002, .005, .010) do you use in search of the “perfect” seating depth?
      .005”

      7) Last question: Do you determine seating depth before or after powder charge?
      Powder Charge first. VLDs jammed .015” into the lands.

    • #1843

      I do no this every rifle chamber with different bullets has their own sweet spot for seat depth and one will have to some testing to find that sweet spot.I understand you are looking for a place to start with seating depth and you may find it right off if not don’t give on that bullet or bullets until you have tried them all at different depth’s.Also chambering a round with little neck tension could change your seating depth if you chamber that round hard and fast or let the bullet bump the feed ramp when chambering a round.I always like to push my rounds in with my finger before pushing my bolt forward.Hope this helps……

    • #1847
      Al Barr
      Participant

      Real interesting info here. Very much appreciated.

      One question for Tony regarding hybrid bullets: If one starts at a .015 jump, does one experiment with longer or shorter CBTO or both?

      Thanks, Al

    • #1855
      Tony Graham
      Participant

      Al,
      I have not played w/ the Hybrids much to date. I will work a load up for my Son’s Dasher over the next does not matter. The theory is that you can start out shooting .015” jump and as the throat erodes you do not have to chase the throat. .015”-.060” jump. http://bulletin.accurateshooter.com/2013/01/berger-hybrid-bullets-what-you-need-to-know/
      I would do 2 rounds set at .015” jump and find your best powder charge. Then do 2 rounds each as follows:
      Touch
      .005”
      .010”
      .020”
      .025”
      .030”
      .035”
      .040”
      Bobby McMichael (IBS 1K Shooter) from over here says his Dasher likes the 105 Hybrid at .040” jump.

    • #1856
      Tony Graham
      Participant

      I am going to try some .30 cal 230 gr. Hybrids this next week in my Heavy Gun at .015” jump to see what the HG will do. I’ve got some brand new brass, so I’ll be running 5 shot groups. Box says 10 twist or faster, we’ll see if the 11 twist will spin them fast enough.

    • #1866
      Al Barr
      Participant

      I appreciate you Tony.

    • #1882
      Tony Graham
      Participant

      Al, you are welcome. Hopefully you can find a load for the Hybrids. The reason I said 2 round groups, was if it will not do it in 2, it damn show want in 5. Good luck!
      Tony

    • #1892
      Al Barr
      Participant

      I’m not at the expertise levels of you folks; but if I am “jammin”, my final determining factor is chambering an unprimed, sized case with bullet seated at the CBTO that I “calculated”. Avoids (for me) increasing clambering efforts and dumping powder into the action when extracting loaded rounds and leaving the bullet in the barrel.

    • #1884
      Wynne Echols
      Keymaster

      Al, I have 2 cents worth that I would like to spend on #4 & #5. Another interesting way to determine OAL is with a hornady modified case and their guage along with a 4′ wooden dowel and the bullet of choice. Remove bolt, place modified case on guage and insert bullet of choice into modified case, ease into chamber with bullet back in case, ease bullet forward until it touches the lands, now stick dowel through muzzle end and push the bullet back a little, now without tightening the hornady guage take one hand on guage and the other end on dowel and push back and forth until you are satisfied with the touch, tighten the screw on the guage and remove the guage, case, and bullet from chamber and take your measurement. Repeat until you are satisfied with your number. As far as seating depth and pressure, I have found out that pressure and velocity do whatever together. More jam will increase pressure and will generate more velocity. As you decrease the jam say all the way to ‘at the lands’ the velocity will decrease proportionally and as you come out of the jam and start to jump the pressure will begin to pick back up the more the bullet is forced back into the case and begins to compress the load. All of this is fun to watch while shooting through a chrony. I have no experience with the hybrids, but sure would be interested in the results of your findings. WWE

      • This reply was modified 6 years, 2 months ago by Wynne Echols.
      • This reply was modified 6 years, 2 months ago by Wynne Echols.
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