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Thread: Loading depth etc

  1. #1

    Loading depth etc

    Hi,
    just cut into the neck of a resized 270 win case, place a 150 grain bullet in then closed the bolt on it softly, pulled the bullet out, changing the bullet every 3 measurements.

    After 15 measurements I took the average as my distance to lands.

    I repeated the exercise with a 130 grain Hornady Interlock and got that distance.

    I have also taken the max and minimum loading data from 3 manuals for the bullet weight and powder to be used and averaged the data given for my min and max loads.

    I want to make up a batch of ammo, loading 5 rounds each at 0.5 grain increments to see which one gives the best grouping.

    After I have that data I want to work out how far from the lands I need to seat the bullet for best accuracy.

    As regards my starting distance from the lands, would you advise 0.030" or the often mentioned 0.015"?

    Regards

    Ian

  2. #2
    Personally I start with the bullet touching the lands. Depending on the bullet in question they seem to like anything between .030 jump to .010 into the lands. funnily enough, all mine like to be either touching or .010 in. If you start off the lands and work in to find accuracy you might find that the pressure spike that results in getting into the lands combined with your chosen powder charge creates pressure problems. If you work up a load with the bullet touching you can always back off to find more accuracy without the danger of excessive pressure. Just my logic and it seems to work well. No doubt someone else will disagree!

  3. #3
    If you're talking a hunting rifle, why not start at magazine length and work inward? If for single loading do as you please.~Muir

  4. #4
    Quote Originally Posted by NigelM View Post
    Personally I start with the bullet touching the lands. Depending on the bullet in question they seem to like anything between .030 jump to .010 into the lands. funnily enough, all mine like to be either touching or .010 in. If you start off the lands and work in to find accuracy you might find that the pressure spike that results in getting into the lands combined with your chosen powder charge creates pressure problems. If you work up a load with the bullet touching you can always back off to find more accuracy without the danger of excessive pressure. Just my logic and it seems to work well. No doubt someone else will disagree!
    You've experienced this? Or is it intuitive reasoning?~Muir

  5. #5
    I'm by no means an expert, far from it, but I took the advice to seat 1 calibre depth, which in my .243 works out to be exactly 2.7000" C.O.A.L, and also happened to group sweet with the right powder charge (I've no clue how far off the lands this is BTW, but fits in the magazine). I have to admit I contemplated on doing it the hard way, ie. starting at the lands, then gradually increasing the seating depth whilst also varying the powder charges, but when I calculated the amount of rounds I'd have to test, I thought "sod it!"..ie. I was trying 34.5g, 35g, 35.5g, 36g, 36.5g, 37.5g and if that was done with say 4 seating depths at 5 rounds a pop, I'd be looking at 120 rounds! and that was before I started testing .25g increments/reductions in powder charges, which could have made it in excess of 250 test rounds!!!!! and THAT was before experimenting with more than one powder, and more than one type of primer!!!!!!!

    So! not wanting to waste 1000 rounds of materials, I decided to stick to 1 calibre depth, and just find the right powder charge given the materials I had bought, and guess what, I found it, and clover-leaf's nicely with all bullets touching each other,,cannot really argue with that..and to be honest, this is MORE than adequate for shooting fox and roe, so unless I plan to start shooting competitively (in which case I'd need to spend another 5K on custom rifle and good scopes), I don't see any reason to go overboard on the accuracy side of things - I could have seen myself tearing my hair out testing numerous seating depths, as well as spending a small fortune! - LOL..just my thoughts...

  6. #6
    Quote Originally Posted by Muir View Post
    If you're talking a hunting rifle, why not start at magazine length and work inward? If for single loading do as you please.~Muir
    This is exactly what I do. JC

  7. #7
    Quote Originally Posted by JC275 View Post
    This is exactly what I do. JC
    But being careful not to start so far out (even though still within magazine capacity), that there's so little of the bullet in the neck that it can come loose or get stuck behind in the chamber when emptying the rifle unfired (more likely if you're loading really light bullets that may be shorter in AOL).

  8. #8
    Quote Originally Posted by PKL View Post
    But being careful not to start so far out (even though still within magazine capacity), that there's so little of the bullet in the neck that it can come loose or get stuck behind in the chamber when emptying the rifle unfired (more likely if you're loading really light bullets that may be shorter in AOL).
    Thats a fair point, I had a rifle once that shot best with the bullets touching the lands but this meant that they were only just in the necks, a few times they got pulled when extracting a live round, powder everywhere and out with the collapsable cleaning rod to tap the bullet free. Not worth the hassle. JC

  9. #9
    Being relatively new to reloading, and just trying out loads on my new (to me) .308, I am interested in why increasing in small powder increments is condidered to affect grouping by some folks?

    In the Lee book and the Lyman one, which i own, both state that seating depth is the major factor in accuracy, do you not agree?

    Simon
    Blindness to suffering is an inherent consequence of natural selection. Nature is neither kind nor cruel but fiercely indifferent.

  10. #10
    Quote Originally Posted by Muir View Post
    You've experienced this? Or is it intuitive reasoning?~Muir
    Just intuitive reasoning. Well known that going from jump to no jump/in lands leads to a significant pressure increase. I didn't want to take that risk so logic said start at the lands. Seems to work for me as I have never had a pressure problem and have achieved good accuracy with some fairly hot loads having played with seating depth after having decided on a powder charge - but I did say someone would disagree!!! I stand to be corrected.

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