• Frank's Lesson's Contest

    We want to see your skills! Post a video between now and November 1st showing what you've learned from Frank's lessons and 3 people will be selected to win a free shirt. Good luck everyone!

    Create a channel Learn more
  • Having trouble using the site?

    Contact support

A-Tips, Jump, and Seating Depth...

Wannashootit

Gunny Sergeant
Full Member
Minuteman
  • Sep 3, 2010
    2,197
    531
    FL
    Trying to find the "balance" here.
    With 300 gr. A-Tips and CIP spec .338 Lapua chamber- seating "to the lands" results in the bearing surface of the bullet just above the boattail roughly at the CASE/shoulder junction.

    Been digesting the latest article on PRB related to seating depth and jump- which flies in the face of what most of us had previously been told which was jam, or minimal jump with VLDs.


    Seating to "optimal" depth- with the top of the boattail just below the NECK/shoulder junction is giving me an OAL a few thou shy of 4".
    Needless to say, never gonna mag feed- and I'd need to throat the chamber approx .250 just to load to the lands- adding for jump would currently be in the .300 range. That's a whole lotta freebore.

    So trying to determine first, whether seating the bullet this deep (with the bearing surface down at the shoulder/case junction) would be compressing the load (91 gr H1000) excessively- and this is with NO jump. Jumping .040-.050 as recommended would shove the bullet that much further into the case.

    If the recommendation of the gurus here is to throat it- how much? Seems one would want to seat the bullet somewhat deeper than "optimal", so that as the lands are chased I still have the full length of the neck on the bearing surface of the bullet?

    What's the advice on how to approach this?
     
    Yeah.
    Been using 285 ELD's- had been seating them with about 20 thou jump- and that placed the top of the boattail just under midway between neck/shoulder and case/shoulder. Obviously not optimal, but the A-tips are seating even deeper.
     
    Lots of cartridges shoot great with the bearing surface below the neck/shoulder, don’t get too wrapped up in that. The lapua, even in the new CIP guns with the 3.8” mags, has always been too long a case for the longest bullets to mag feed unless you plan to single feed, which is an option for you. Load it up and shoot it, then go from there.