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Tim 1....this is absolutely the truth. However, I think it is most obvious in the smaller calibers. I've had groups shrink from barely moa to well under that figure mostly from moving closer to the lands, BUT you must be careful moving the bullet forward s pressure can spike...always drop the powder amount a bit and work back up. There are a lot of things at work here. | |||
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one of us |
I agree. I have seen times when moving the bullet in and out seemed to have absolutely no affect, and others where it made all the difference in the world. I also agree that you see the most change in the smaller calibers. I tend to do my loads this way. Be assured it is not the only way of doing things, just the way that has worked well for me. I like to start off with the bullet .030" off the lands with conventional lead core bullets, .050" off with the Barnes X or solid. I proceed to find my best load, then start monkeying around with seating depth, varying the depth by .003". If at max load then I go .002". Some like to go more, some less, but by using .003" I have not seen any great unexpected increases in pressure. Of course, all of this is academic if you mag well sets the length of your cartridges. In my 458 Win, 7mm STW, and 300 Wby, forget about getting anywhere near the lands. The throats are so long and the mags so short in the 458 and 7mm, all I can do is seat them out as far as possible and let 'er rip. While the 300 is a single shot, the throat is so long in that one that to get anywhere near the lands there is no bullet left in the case! | |||
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| one of us |
My experience has been that seating depth contributes more to accuracy than any other variable. I've seen tremendous improvements by varying seating depths, so much so that my usual load workup now consists of settling on a powder that gives good velocity at low pressure then varying the seating depth to get the best accuracy. It usually works for me. I haven't found much difference in accuracy between different powders in the calibers I load. | |||
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| <DuaneinND> |
I pick the powder I want to shoot, the bullet I want to shoot, and then I tune the load by the seating depth. This approach will work with 99% of rifles with a custom barrel and 75-80% of factory rifles. This is not saying that this is the ultimate accuracy the rifle is capable of, but for the bullet and velocity I want to use for the purpose intended. | ||
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| <aussie john> |
My Rem700 in 270win has a fair amount of lead and 130gr bullets go nowhere near the lands, so I seated the bullets to .250 in, and increased the neck tension a little. I now settle on an OAL, then slowly work up the powder in .5gr increments until the best accuracy/pressure is found then I chronograph the load. Most of these loads are not the fastest loads available, but the velocity spread is usually no worse than about 15fps.(fastest to slowest) Accuracy usually runs an inch or a bit less at 100yds. So this is how I do most of my loading with rifles that can't seat the bullet close to the lands. My view is that seating depth is only one of the very many varibles in the accuracy equation. | ||
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one of us |
Anything that affects the harmonics (vibrations) of the barrel, affects accuracy, whether it be seating depth, propellant charge, primers, or weight at the end of the barrel, such as a BOSS system. Any changes in any of these combinations can and does affect accuracy. | |||
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| one of us |
Why not seat .010" off the lands, if mag box allows, then work up the powder charge to reach velocity/pressure you desire? Mike ------------------ | |||
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| <10point> |
Seating depth is critical to acheiving "maximum accuracy" but not so much "acceptable accuracy". Many feller's buy a box of ammo, they see it prints halfway decent, and then they firgure the hell with it ; Its good enough. Us obsessive/compulsive types arent happy until we reach accuracy nirvania with a rifle. Its here that seating properly, and repeatably, is so important ; Tho its only one componant in getting the best accuracy. Generaly my first chore is to find the right load, and seat, for a particular rifle. A few rifles I was lucky enough to find a super accurate factory load and then I just duplicated the seat of that load. I think the RCBS "screw together" micrometer's are the best..........10 | ||
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| <aussie john> |
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| one of us |
Based on the stunningly scientific data of 'Aw I've got my new rifle, I want to fire it and I haven't got the time/desire to get the Stoney Point out' I put together a gradualy increasing set of loads with Hornady RN bullets in my 7x57 seated to the cannelure. Checked the bullets weren't touching the lands and off I went. Result 2 touching. Repeated to check not a fluke. Unfortunately on both occasions I made scope adjustments (as I was going stalking next and was running low on ammunition) and the first shot on both was 7/8" off due to delayed adjustment on the scope (scouts honour) Turns out the bullets are about 100thou off the lands! I have heard other people say that RN bullets are less sensitive to seating length. | |||
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| One of Us |
My A-Square Reloading Manual says sometimes it does, and sometimes it doesn't. ASRM says seating depth does matter if your rifle has a tapered throat (section of barrel beyond the case mouth and prior to the commencement of the rifling). In such a rifle, you want the bullet close to the lands, because you don't want it wobbling around off the bore axis and entering the rifled part of the barrel other than parallel to the bore axis. ASRM says seating depth does not matter at all, not even a little bit if the throat is parallel (does not taper). Whether or not the chamber throat is tapered is a function of the cartridge the rifle is chambered for. The throat configuration is part of the specifications for a given caliber. A .300 Weatherby Magnum chamber has a parallel throat, and a .404 Jeffrey chamber has a tapered throat. A tapered throated .300 Weatherby or a parallel throated .404 Jeffrey would be a nonstandard rifle, and if you've got one, someone special ordered a nonstandard reamer to chamber that rifle. I'd like to find a database of cartridge specifications that does include throat configuration. ASRM doesn't have this data for all the cartridges listed, as far as I can tell. | |||
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| <PowderBurns> |
Powder and bullet combination may be the LEAST critical variable in reloading for accruacy. Seating depth and seating the bullet optimally against the lands is important. But so is case concentricity, neck tension, neck length/squared, finished, flashole deburring, primer pocket uniformity, primer seating. In a bolt gun it's possible to single load the ammo. So OAL really doesn't matter unless you're looking to fill up a magazine. (My Rem 700 has a "block" in the magazine. I wonder if I can get away with removing it.) Remingtons are long throated. One solution to this is having a smith shorten the chamber end of the barrel and rechambering -- while punching out to Ackley for instance. This often means moving the recoil lug. It can get expensive. For all the accuracy of the Rem 700, I find that coyote hunting I use an AR with a 6x scope and "cranked out" mixed brass reloads without a lot of prep. I get MOA, and the yotes don't much care . . . ------------------ | ||
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| <aussie john> |
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| <aussie john> |
Most of the time I do load as close to the lands as possible and work up the powder charge accordingly. But, if the rifle has a fair amount of freebore to the lands and therefore the bullet only just reaches a close seating arrangement with minimal bullet seated in the case and still has magazine room to spare,(eg. the particular Rem700 I refered to), then some other matters come into play, especially if one is to be hunting big game and the rounds are loaded from the magazine. A bullet that is seated close to the lands but misaligned through the action slamming it into the chamber for a second shot through whatever reason, is most likely not going to be as accurate as the load developed with a reasonable amount of bullet in the case neck, holding it firm with the same neck tension and alignment as the previous round. Great to sit on the range and single load, but when hunting and conditions are not perfect, I'll go with a little less accuracy and take reliability every time. Hope this explains my earlier comment a little better. Keep safe, from the far side John [This message has been edited by aussie john (edited 09-05-2001).] | ||
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