Measuring Bullet Seating off the Lands

Discussion in 'Reloading' started by ntrl_brn_rebel, May 20, 2010.

  1. ntrl_brn_rebel

    ntrl_brn_rebel Member

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    Most of my reloading career I have more or less went off recomended COAL. Im working up some loads with Berger 185 VLD's and having little luck in getting them to group very well out of my Sendero 300RUM. I have had the same luck with heavier VLD's and want to give them an honest effort as I have had GREAT luck with them in the past in other calibers.
    When Berger recomends holding them off the lands, how exactly do I measure this (.020 or whatever), this might be a dumb question but Im a little stumped??? Im what I consider a NEWBIE at this longrange reloading stuff so bear with me. Thanks ahead of time.
     
  2. pablo

    pablo Active Member

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    I read an article explaining how to adjust seating depth for Bergers on the Berger web site. Check it out.
     

  3. MSLRHunter

    MSLRHunter Well-Known Member

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    The first thing you need is a comparator to accurately measure oal. Berger bullets can vary substantially in length due to the hollow point, so simply measuring the length of the entire bullet will cause your oal to be inconsistent. Next, the oal tool from hornady is best but you can use the old trick with a bullet colored with a marker if you don't want to purchase the tool. The tool simply gives you a way to measure the length of a cartridge when the bullet is pushed up against the rifling, so you can then set your seating die for the bullet to be the desired distance from the rifliing. For example, my 300win mag with 210 vld shoots best at 0.025 off of the rifling. I hope this helps, I am sure others will chime in with more useful tips.
     
  4. Len Backus

    Len Backus Administrator Staff Member

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  5. FEENIX

    FEENIX Well-Known Member

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    I find this very helpful, give it a try ...

    Real Guns

    Good luck!

    Ed
     
  6. Take a small round file and file a slot in the middle of the case neck all the way down to the shoulder. Size the case and slide in your bullet just enough so it stays put. Chamber the round and the rifling will seat the bullet. Measure the ovarall lenght. Pull the bullet part way out and do this three or four times and measure the overall length each time. This will show you how long the round must be to touch the lands., Load some right at that length, some at .02 shorter and some .04 shorter than that length. Shoot some groups and see what your gun likes.
     
    Last edited by a moderator: May 21, 2010
  7. boomtube

    boomtube Well-Known Member

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    Let me offer some perspective on the good stuff above.

    First, underatand that finding the precise OAL to the lands for each bullet is much less critical than some seem to think. I have all the tools for measuring max OAL and tried using each, including averaging the results to reduce effective errors on my part. Finally realized I was chasing a meaningless dimension. I've gone back to the marked cleaning rod (a wooden dowel actually). It's plenty precise and I only do it once, no averaging.

    All we need to do is find a close approximation (if that) to use as a reference starting OAL. From that, we will back off until we find the best shooting point. I start seating tests from about 15 thou off the lands so any ogive to lands accuracy better than +/- 10 thou instantly becomes meaningless, it's just a reference point with no other value.

    I do my seating tests in 5 thou steps until I find the best shooting depth. Final results can easily vary from .015" to as much as .100" off the lands, thus measuring to a specific starting distance off the lands within +/- half a gnat's azz is pointless.

    You will likely find the "best OAL" is NOT a specific point. More likely it will be a range several thousants wide in which accuracy is the same. Seat in the middle of that range and later tiny variations in seating and throat errosion won't mean a thing. Seat on the ragged edge of that range and your loads will be quirky no matter how precisely you made the starting measurement.
     
  8. joe4570

    joe4570 Member

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    Or maybe the dynamic is not so much related to the physical distance from the lands or leade in terms of bullet support, but rather to the change in case volume caused my moving the bullet into or out of the case and the associated change in start pressure.
     
  9. boomtube

    boomtube Well-Known Member

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    Joe. you may be right, I don't know. But, transfering the concept to the carrridge requires an adjustment to the OAL.
     
  10. Yotebuster

    Yotebuster Well-Known Member

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    The problem you will run into , if it is a problem for you, Is seating the bullet touching or even .20 thous off the lands, you will not be able to get your cartiridge in the magazine, It's too long, Especially with Bergers, I load mine for hunting so I want to be able to put more than 1 in the gun at a time. Unless of course you have had the barrel set back/ or extended magazine installed. I have to have mine .80-.90 usually on my guns from the lands to get them into the magazine. I have the Hornady tool, Works well for intended purpose, But hasn't done me much good wth the Bergers., with them being soo long and all.
    Dan
     
  11. Len Backus

    Len Backus Administrator Staff Member

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    Boomtube
    Lately I have assumed that position, too. Especially in light of Eric Stecker's article on OAL and its relationship to seating relative the location of the lands with VLD bullets.

    So I agree that perfect accuracy in measuring the location of the lands is not essential. That is a relief to me since I have never been as confident as I'd like when using any of the measuring tools or methods.
     
  12. joe4570

    joe4570 Member

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    Not necessarily, although I always work up loads with an OAL gauge and a comparator. The Stony Point (Hornady) gauge is inexpensive, reliable and easy to use. Of course the second COL check, as already pointed out in this thread, is making sure the cartridge also clears the magazine, feeds up the ramp and, hopefully, ejects as an assembled round. For me, use of the gauge is to assure consistent assembly and safe operation.

    One advantage the Hornady unit has over some of the home brewed OAL gauges that are based on slip fitting a bullet into a case neck is that measurement is controlled by a pushrod that passes through the case. So if the lands grab the bullet and pull it forward when extracting the gauge, this is corrected when the bullet heel is seated back against the pushrod when the measurement is taken.

    Bullets with extended ogives often make getting near the lands impossible as bore diameter is reached so far up from the bullet's nose, a cartridge assembled to 0.020" off the lands would be too long to cycle through the gun. When I load for the .300 UM I don't exceed 3.600" and finesse charge for accuracy. A 0.020" movement that results in a 500 psi shift in pressure can be duplicated with a 0.2 tenths grain change in powder charge with a similar impact on accuracy as would result from moving the bullet toward or away from the gun's lands. I know we all have our own theories to apply for maximum performance.

    Just a thought.
     
  13. Michael J. Spangler

    Michael J. Spangler Well-Known Member

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    alright i'm new to this so bare with me.

    do bullet seating dies seat by pushing down on the tip of the bullet or on the part that is the diameter of the bore?

    i've been trying to find some info on this and i guess i'm not wording it properly so i'm not getting good results from the search function.

    if the die seats based on the tip then we wouldn't be able to control proper distance from lands without all kind of fiddling.

    but if it seats from the major diameter of the bullet, then it would be repeatable, and consistent, completely ignoring the difference in base to tip length right?

    and i guess another questions is, do all dies work this way? or only some?
    thanks for the help guys. this forum is a super wealth of knowledge and source of trouble for me, i keep wanting to buy more things and shoot more.

    i just can't see using my newly acquired .300RUM and not reload it to it's potential

    thanks again guys
     
  14. LRHWAL

    LRHWAL Well-Known Member

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    Michael,

    The seater plug will (or at least should!) contact the bullet somewhere near the ogive and not on the tip. It's not as low down on the bullet as the "bore dia". Some of the VLD type designs will sometimes bottom out against the bottom of the plug hole and then the plug should be modified (the hole enlarged or drilled deeper). As far as my experience goes with the brands of dies I've seen, they all work this way.

    Boomtube,

    Nice description. I've also tried numerous home brew techniques. I use a Stoney Point (Hornady) now, but all have their problems. That was a great discussion of how to do it practically and maintain your sanity...