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Thread: Tuning handloads for seating depth

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    Default Tuning handloads for seating depth

    So, how many of you handloaders tune your loads for seating depth, trying different lengths to obtain better accuracy?

    Is it usually worth the trouble, and how do ya actually go about it?

    I don't do it, so I've no bone to pick. Just askin.

    Thank You, for your take on this.

    Smitty of the North
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    I may be backwards from "right," but after 50 years of reloading I doubt I'll change to make someone else happy.

    First thing I establish before any loading at all is max OAL for that bullet in that rifle using an unprimed case and seated bullet. I.e., I'm seeing how far out I can seat the bullet without touching the lands. Then I compare that with mag length. If the mag is long enough that's it. If it's too short, I'll seat the bullet deeper till it clears the mag. Now I label the case as to bullet, wt, and rifle using an engraver when I can find it, the tip of my pocket knife when I can't. Now I've got a dummy for that bullet and rifle. I tried leaving them all in a drawer (I have hundreds accumulated over the years) but that got unmanageable. Now I put them in the box with the die set for that particular caliber. Lots of rattling when I open the drawers with dies in them, but at least it beats rattling through a big bunch of rounds loose in a drawer.

    Here's the backwards part: I never bother going shorter than either of those lengths looking for "better" groups. I can usually get performance to satisfy me simply with powder/primer adjustments using the established OAL. If I was shooting matches maybe I'd explore deeper seating if nothing else worked. But for hunting I could give a rip for another 1/4" off a group, much less 1/64".

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    Quote Originally Posted by Smitty of the North View Post
    So, how many of you handloaders tune your loads for seating depth, trying different lengths to obtain better accuracy?

    Is it usually worth the trouble, and how do ya actually go about it?

    I don't do it, so I've no bone to pick. Just askin.

    Thank You, for your take on this.

    Smitty of the North
    So long as the ammo is otherwise consistent, I've found tailoring OAL is the key to finest accuracy. I do not mind powder charges varying .1-.2 grains per charge weight in '06 cases or larger, but I want my handloads to have a very particular and very consistent OAL. Barrels and chambers vary, but as a rule I've found best accuracy either in, or very close to, the lands. Barnes X, XLC, TSX, TTSX being an exception to the rule. Depending on magazine constraints and the rifle's purpose I'll load as long as possible and if accuracy is less than I desire I'll experiment from there. I've recently been testing some 130 TSX bullets in a 270. RL 22 will push them a little over 3100 fps, but it has taken quite a few rounds to develop an accurate load in this rifle. I'm satisfied right now and OAL is 3.490 for a jump of 0.035. Seated in the lands, that load was okay, but by adjusting seating depth I've made some significant improvements; more than 1 MOA. The same rifle is very accurate with NBTs, but they like to be in the lands.

    For me, adjusting OAL is key to my load work.
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    I have tried it on several rifles without any apparent improvement. Now I just back them off the rifling about .020 if they will fit in the magazine. If they won't fit the mag, I shorten them until they have .015/.020 clearance.

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    I do what rbuck does. Usually with hunting guns, I run out of magazine length before I run out of throat length. It is interesting to buy a Hornaday seating depth gauge and find out how far you can run the bullets out. But, like I said, usually, the magazine is the limiting factor. If your barrel throat is the limit, then try seating to .015 to 020 inches off the lands. Typically that will get best accuracy out of a hunting rifle without running into a problem with feeding due to friction with the magazine and bullet tips.

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    Quote Originally Posted by 1Cor15:19 View Post
    Barrels and chambers vary, but as a rule I've found best accuracy either in, or very close to, the lands. Barnes X, XLC, TSX, TTSX being an exception to the rule.
    Nosler E-tips also like the longer jump to the lands. My 300 wsm seems to like them with a .075 jump though I've heard of others needing up to .10 to tighten up the groups.

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    Thanks guys:

    I could work with that. I usually seat .030 off the lands or magazine.

    If nothing else worked, I could seat them shorter to see if they're more accurate. I jist never tried it.

    Thanks Again
    Smitty of the North
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    Smitty
    The theroy here is that the closer the bullet is to the rifling the less chance it has to start in the rifling off center. My idea has been that the tighter the case fits the chamber the less chance it has to be pointed in the wrong direction to start with. And of course, the better fit the throat the less chance of starting the bullet askew. So, if you are neck sizing or partial FL sizing, this leaves no slop in the head space and the tapered shoulder can only center itself with no room for sideways play. Another thing I think helps is by partial FL sizing you leave a little of the neck unsized which should make for an almost perfect fit of the bottom of the neck to the chamber neck area. Also partial sizing shouldn't shrink the case much just ahead of the solid part of the case head. Leaving that part full chamber size should center it very well. Now, with the case well centered and the bullet fitting the throat well, it shouldn't matter whether the bullet jumps .090 or not at all. Anyway my limited testing has not shown accuracy differences between short or long loaded rounds provided the case and bullet fit right. Also if the case is loose in the chamber it seems to me it could start askew whether loaded short or long. Anyway, that's my ideas on the subject for whatever they are worth.

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    Start with seating them as long as the magazine will allow. You can't go any longer than that anyway unless you are using single shot. Then you only have one direction to work in and that is seated deeper in the case. In my Pro-Hunter I will mess with the seating depth because it's a single shot but I don't mess with it much on bolt guns. I concentrate on powder/primer combinations.
    "...arms like laws discourage and keep the invader and plunderer in awe...Horrid mischief would ensue were the good deprived of the use of them." -Thomas Paine

  10. #10

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    The closer to the lands you are the more consistant the starting pressure is because the lands are the most signifacat resistance to bullet movement. Verying the OCL tunes the load to the barrels viration nodes as does powder and primer varients.

    Remember the highest pressure is with the longest OCL on bottle neck cartridges so always work up to the max pressure load with the longest OCL. As you shorten the OCL the pressure goes down.

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    Quote Originally Posted by tjen View Post
    As you shorten the OCL the pressure goes down.
    That cornfuses the heck out of me.

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    Quote Originally Posted by tjen View Post
    As you shorten the OCL the pressure goes down.
    That is not accurate enough to be a blanket statement. I've had velocity increases and decreases when getting further from the lands. Each load is truely one of a kind.

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    Quote Originally Posted by tjen View Post
    As you shorten the OCL the pressure goes down.
    Quote Originally Posted by marshall View Post
    That is not accurate enough to be a blanket statement. I've had velocity increases and decreases when getting further from the lands. Each load is truely one of a kind.
    Gotta agree with marshall on this one. I've had loads go back and forth with the pressure issue. A couple of no-brainer illustrations: if the round becomes excessively compressed due to a shorter OAL you can experience a spike in chamber pressure or if bullets are seated into the lands there will be a spike in chamber pressure as well. You can get higher pressures with ammo loaded shorter or longer.

    I do agree with tjen, that seating closer to the lands is typically more accurate, sometimes significantly so, but can't agree about his blanket statement concerning its effect upon chamber pressure.
    Foolishness is a moral category, not an intellectual one.

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    Normally as case volume goes down, pressure goes up. But pressure can also go up when you start getting close to the rifling. Powder, primer, bullet weight, bore size, oal, case volume and who knows what else all contribute to initial pressure and how consistant iginition is. I'm sure that in some rifles with certain bullets oal makes a noticable difference, but I'm just as sure that in other rifles with certain bullets it makes little if any difference as far as accuracy is concerned. There's plenty of rifles that shoot very well with mag length oals that are quite a ways from the lands. I have a 700Rem short action n 350Rem that I can't get close to the rifling with because of the mag. It shoots 5/8" to 3/4" with a variaty of loads.

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    Quote Originally Posted by tjen View Post
    The closer to the lands you are the more consistant the starting pressure is because the lands are the most signifacat resistance to bullet movement. Verying the OCL tunes the load to the barrels viration nodes as does powder and primer varients.

    Remember the highest pressure is with the longest OCL on bottle neck cartridges so always work up to the max pressure load with the longest OCL. As you shorten the OCL the pressure goes down.
    I've been reloading for awhile but I have never heard the term "OCL". What is that?
    "...arms like laws discourage and keep the invader and plunderer in awe...Horrid mischief would ensue were the good deprived of the use of them." -Thomas Paine

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    OCL= Overall Cartridge Length. Many people say COL rather than OCL.

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    Quote Originally Posted by evandailey View Post
    OCL= Overall Cartridge Length. Many people say COL rather than OCL.
    Thanks, I usually hear OAL or COAL.
    "...arms like laws discourage and keep the invader and plunderer in awe...Horrid mischief would ensue were the good deprived of the use of them." -Thomas Paine

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    Good discussion fella's, good post Smitty.
    To me I will work on seating depth trials more for fun than anything and definetly NOT for all my guns.
    If I am going to hunt and shoot critters, under say 250 yards, then once I achive decent accuracy, cartridge feeds well, I am satisfied.
    I think one has to have sound reasons, ( or a drive for perfection ), to chase the extreme accuracy efforts. Probably 99 percent of the game we chase is not going to require the effort as long as we are getting 1 -1 1/2in range groups at 100 off a bench.
    I agree with 1Cor - post #3 - if your an accuracy nut it can be the deal maker!
    When asked what state I live in I say "The State of Confusion", better known as IL....

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    Quote Originally Posted by BrownBear View Post
    I may be backwards from "right," but after 50 years of reloading I doubt I'll change to make someone else happy.

    First thing I establish before any loading at all is max OAL for that bullet in that rifle using an unprimed case and seated bullet. I.e., I'm seeing how far out I can seat the bullet without touching the lands. Then I compare that with mag length. If the mag is long enough that's it. If it's too short, I'll seat the bullet deeper till it clears the mag. Now I label the case as to bullet, wt, and rifle using an engraver when I can find it, the tip of my pocket knife when I can't. Now I've got a dummy for that bullet and rifle. I tried leaving them all in a drawer (I have hundreds accumulated over the years) but that got unmanageable. Now I put them in the box with the die set for that particular caliber. Lots of rattling when I open the drawers with dies in them, but at least it beats rattling through a big bunch of rounds loose in a drawer.

    Here's the backwards part: I never bother going shorter than either of those lengths looking for "better" groups. I can usually get performance to satisfy me simply with powder/primer adjustments using the established OAL. If I was shooting matches maybe I'd explore deeper seating if nothing else worked. But for hunting I could give a rip for another 1/4" off a group, much less 1/64".
    What he said. I seat the bullet just so it clears the lands and will fit in the magazine. If it shoots reasonably well, say 1.5 MOA I'll spend the time practicing off hand. If it doesnt shoot well I'll play with different powders and bullets.
    Tennessee

  20. #20

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    Quote Originally Posted by AKHunterNP View Post
    I've been reloading for awhile but I have never heard the term "OCL". What is that?
    I type with two fingers sometimes they get out of order from my brain or I fat finger a key next to the one I was aiming for. Guns are so much easier to use than key board for me.

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