How to find best seating length?

Discussion in 'Reloading Forum (All Calibers)' started by chevytruck_83, Apr 15, 2018.

  1. chevytruck_83


    Mar 24, 2011
    Whats the best way to find the seating depth your gun likes while keeping round count down? I enjoy testing hand loads but realize now with a fast shooting 6mm I’ll have half of my barrel life used up till I’m happy.
  2. Dusty Stevens

    Dusty Stevens COVFEFE- Thread Derail Crew

    May 8, 2014
    start out jammed that way you can only go one way
  3. krummarine

    krummarine Silver $$ Contributor

    May 7, 2008
    I start with .020 off the lands. Best of both worlds.
    bouddha likes this.
  4. JBO

    JBO Gold $$ Contributor

    Jul 2, 2012
    + 1
    ljmontano and Don like this.
  5. DirtySteve

    DirtySteve Gold $$ Contributor

    Jan 22, 2017
  6. Steve Donlon

    Steve Donlon Gold $$ Contributor

    Aug 9, 2017
    I agree with Dirty Steve and
    Berger bullets. Jamming a bullet is the easy way if you can but there are many downfalls to this method. If the the bullet is straight in the neck it will fly straight. Many rifle have chambers too long to jam. It's more important to have enough of the bullet in the neck to load it straight by what ever means you think works best for you. At last that's what I've seen from decades of reloading accurate rounds without a lot of fancy tools. But I don't compete and worry about 1/8th groups.
    DirtySteve likes this.
  7. rhovee


    Dec 31, 2017
    I start at .020 off most of the time. Then shoot a ladder over a chrono. Even if the seating depth is off you can get a pretty good idea of powder charge. Then take that charge and adjust closer and further and see if things get better or worse. I just found the best seating depth was .030 off even though the bullet is known for shooting good at .010 off. If your powder charge is in a "scatter node" seating depth will be hard to find...
  8. ShootDots

    ShootDots Gold $$ Contributor

    Jan 9, 2008
    There are some "generally accepted" places that certain bullets like to be. MOST VLD's like to be IN the lands. I like to start out with VLD's right at 12 thousandths INTO the lands. Then find a good powder charge and possibly adjust the seating depth to some degree. Most of the Tangent Ogive, what we consider "Boat Tail" bullets, like to be OFF the lands somewhere. Generally, I start them at 10 thousandths off to see if I can find a good powder charge, then adjust the seating depth if necessary. I have found Berger Hybrids like to be somewhere between 15 and 20 thousandths OFF the lands. I normally start them at 17 thousandths off. NOTE: there are some exceptions to these "generally accepted" norms of where certain bullets like to be seated>>> Two off the top of my head is the Berger 6mm 108BT, which generally likes to be about 7 thousandths INTO the lands, AS DOES the Berger 6.5 140 LRBT (Long Range Boat Tail).. Now does that mean these are "Hard and Fast" rules? >> No it does not. However, they are really GOOD places to START!
    NOTE: VLD's used for HUNTING should NOT be jammed into the lands. Berger has a "seating depth finding method" that should be used for rifles used for hunting and that have magazines. These can be mitigated to some degree with longer than "normal" bottom metal and the correct freebore used on the reamer.
    SPJ likes this.
  9. mikecr


    Nov 26, 2004
    I've always used a version of Berger's recommended seating testing. With this, I have yet to find jam or any other in-the-land (ITL) relationship as best for VLDs(95, 105, 140gr).
    I suppose a lot of this is because I don't shoot underbores that need high starting pressures to shine.

    Speaking of starting pressures, relying on ITL relationships means chasing erosion with seating. Otherwise you reach step changes in pressure(normally dropping).
    Luckily, while best seating is OTL, you will never have to chase lands, and unless competing at short range, long term accuracy is better than fleeting.
    So I recommend finding best OTL, and go with that. Move on to powder development with that.

    It all begins with a bullet. Consider every aspect of a shooting system w/resp to a bullet.
    Pick up a sample amount of a bullet for testing -from a large lot. If it tests well enough, buy from that lot enough for the expected life of that barrel(at least). It's thousands, yes, but bullets are always a good investment.
    Same with brass, same with powder, same with primers.
    Don't put yourself in a tail chasing position, with mixing of any components.
    JBT likes this.
  10. K22


    Jan 24, 2011
    Frankfort Arsenal Tool, available at Midway. Easy to use, cheap, reliable and doesn't consume a case.

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