Load development and seating depth?

Discussion in 'Reloading' started by Dgutter, Mar 30, 2011.

  1. Dgutter

    Dgutter Well-Known Member

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    I'm plannin on developing a new load and through my past reloading I have never been too concerned with seating depth. Usually through charge adjustments I could attain the accuracy I was looking for. I've raised my standards much much higher and realize that seating depth is quite important. So....
    My question is should a guy develop his powder/primer/bullet combo then adjust seating depth or vice versa?
     
  2. lever-hed

    lever-hed Well-Known Member

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    yes, develop cartridge recipe, that will give you a good indication of accuracy, THEN play on seating depth (or oal to lands).
     
  3. Mikecr

    Mikecr Well-Known Member

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    Nope, adjust seating depth first.
    Best seating does not change with powder(amount or type), but powder IS affected by seating..

    I know,,, it's counter to all herd murmuring....
    But hey, you asked
     
  4. Bravo 4

    Bravo 4 Well-Known Member

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    With my bolt guns I agree with what Mike stated, whether they are gonna be mag fed or loaded single shot. I find the max oal then the max load of a given powder, primer and bullet combo.
    With my AR I get the oal that will work reliably in the mag then adjust the powder or primer till I get the accuracy with the bullet I chose. Then change bullets if that doesn't work. There doesn't seem to be a lot of play in workable oal.
     
  5. WV Sendero

    WV Sendero Well-Known Member

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    I've done it both ways but I would agree that it's probably best to do seating depth first because the best depth will likely be the best with all powders. If you think about it powders are highly dependent on case capacity and useable capacity can vary a fair amount when changing seating depths especially with the longer bullets we typically use so it's best to vary you powders after you get your depth (and capacity) set. Chaning seating depths also can change pressures for the same reasons so your max load at one depth may be over max at another.
     
  6. woods

    woods Well-Known Member

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    moooo (making herd murmuring noises)

    The way I do it is to run an Audette at 300 yards. That is to load each case with a progressively higher powder charge. The point of impact will progressively rise and theoretically there will be 3 or 4 shots that level off and group closer. Sometimes it seems to work but it is like reading tea leaves

    [​IMG]

    My main purpose is to find the velocity I want. Then I load sets of 4 or 5 shots at different seating depths to look at the accuracy

    [​IMG]

    Varying seating depth will change the velocity and the timing of the muzzle exit but to a lesser degree than varying powder charge. So IMO powder charge is macro tuning and seating depth is fine tuning.

    IME it is 2 variables both of which have an effect on accuracy and a variation in powder charge or seating depth will change group size and POI.
     
    Last edited: Mar 30, 2011
  7. benchracer

    benchracer Well-Known Member

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    I've done load development both ways, powder charge first then seating depth and vice versa. I am not convinced that it really matters. I have had good results either way.

    More and more, I am convinced that developing a consistent and methodical approach that works for you is more important than what variable you change first.

    FWIW, I do my initial work up using the OCW method found here:

    OCW Overview - Dan Newberry's OCW Load Development System

    Following that, I fine tune my seating depth using the procedure recommended by Berger Bullets for use with their VLD's. I have found Berger's method of tuning seating depth to be effective with a variety of bullets.

    That is my little "rain dance" and it works for me. My advice is to develop a "rain dance" that works for you and tweak as needed.
     
  8. Mikecr

    Mikecr Well-Known Member

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    I think the reason it often works well enough powder first is that some bullet/chamber combinations are not highly sensitive to seating. So seating takes on a relatively minor role there, and is then taken as a minor adjustment.
    Other combinations are just opposite.

    But I still stand behind my order of seating first(even if seemingly minor).
     
  9. benchracer

    benchracer Well-Known Member

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    I would consider that a perfectly valid methodology. I know it to be capable of producing good results. I don't think it is the only way to do things, but it is a good approach.

    IMO, the most important aspect in this is to understand what you are doing and why. Have a plan. Be methodical. Modify your plan as needed.

    However one chooses to do things, the development process should produce repeatable data that tells us what combination will yield the performance we want from our hand loads and do so in the most efficient manner possible.
     
  10. BountyHunter

    BountyHunter Writers Guild

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    I go with powder first also and run the ladders to find my sweet spots.

    However, I set the bullet at either max COAL if a magazine gun or .020 in the lands for a gun shooting VLDs.

    Get the load and then tune for seating.

    You are at max pressure and never have to worry about pressure wehn tuning from there with other adjustments unless you change bullets or primers.

    It works extremely well for max accuracy in LR comp guns, so pretty sure it will be more than adequate for LR hunting rifles.

    As stated though, go with a plan and work it to see if you get the desired results you were looking for.

    BH
     
  11. BradArnett

    BradArnett Well-Known Member

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    This might be contrary to others load work process, but here is mine. It's never not worked for me. I also run moly in everything so that is a given.

    Before I ever load a round I have an idea of what speed range I want to run in the bullet/cartridge I'm working with at the time.

    I find the distance to the lands with the bullet I'm going run and make a dummy round to set my seating die with. Now I'm working with only 1 of 2 possible measurements here, either what I'm restricted to by the mag-box, or putting the bullet in the lands. With all my custom rifles it's working in the lands as I have the rifle throated for the bullet I'm going to run and have it work from the mag-box. Factory rifle's might leave you stuck with working from the mag-box and jumping them. I have no use for a singe-shot bolt gun and I won't make that concession. (personal preference. Nothing wrong with single shooting a bolt gun, it's just not for me.)

    Now I load up single rounds of incrementally increasing charges to run through the chrono. I chrono them looking for my target speed or pressure, whichever comes first. I guess you could call it a "semi-ladder", as I am keeping track of speeds and where the rounds land on target.

    Once I have the chargeweight's that are in my speed range I load a few more for group shooting with smaller charge weight increments around the target speed/charge. I rarely shoot these for groups at 100yds and mostly I do it at 2 or 300yds. Way more often than not I find a good working load during this step and am done except for stretching them out to the max working distance that I plan on using that partricular rifle for.

    I can only think of one time I had to go back and drastically change seating depth's to get a good load and that was with 168gr Barnes TSX's in a GAP built 308. That rifle liked them jumping. I've run Barnes TSX's in the 223/223AI/22-250/270/280/308, that 308 is the only one I've had to jump them, all the other rifles shoot the TSX's very well in the lands. That is also contrary to what Barnes says about their bullets, but I can't argue with results.
     
  12. Ackley Man

    Ackley Man Well-Known Member

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    Adjusting seating depth is traditionally the final step in fine turning a load unless you plan on using a load charge that is running on the ragged edge of maximum simply because seating depth can have a profound effect on pressure. As you probably already know, COAL is a worthless measurement except when applied to magazine clearances. It is a measurement established by SAAMI for use by arms and ammo manufacturers in an attempt to standardize measurements for each given caliber. Unfortunately the specs are not followed as closely as we would like by either of the manufacturers. Seating depth measurements must be based upon a leade (beginning of rifling) to case base measurement. A seating depth gauge is required to establish this measurement in conjunction with the particular bullet you will be using. Each bullet make and style change will require a new measurement because it will be established from the bullet ogive. As a double check for your measurement, equally square lands marks on your bullet will indicate a +.005 into the lands seating. If you intend to use a particular rifle mostly for hunting you probably do not want to seat bullets into the lands more than .005 because if you need to eject a round from the chamber the bullet may stick in the rifling. There is almost nothing worse than dumping a case full of powder into the trigger group. Personally, after I am satisfied with my load based upon selected muzzle velocity I test seating depth with three shot groups, after shooting one or two bore fouler rounds, being sure to allow the barrel to cool between groups. Normally I start with "0" the go to the plus side (+5 & +10) then to the negative side (-10, -20, -30). One of the three shot groups will exhibit smaller measurements. You can then additionally fine tune by going to the + or - side of the best group. Good luck with your testing.