Dead-Length Bullet Seating

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The following is a specially adapted excerpt from the forthcoming book Top-Grade Ammo by Glen Zediker and Zediker Publishing. Now, it’s just around the corner… BuyZedikerBooks.com for details.

by Glen Zediker

Last time I showed a couple of valuable tools: the Hornady LNL O.A.L. Gauge and the LNL Comparator. The first showed the bullet seating depth that touches the lands, and the other gave a more accurate way to measure. Now for a few ideas on how to use this newfound information.

“Dead-length” sounds pretty ominous, and it is, or can be. Again: that is the cartridge overall length that has a bullet touching the lands when the round is chambered.

Hornady LNL O.A.L. Gauge, and why to use it: these three .224 Sierra 80-grain MatchKings are seated to touch the lands in three different barrel chambers. You need to know the overall length if you want to experiment with this tactic.
Hornady LNL O.A.L. Gauge, and why to use it: these three .224 Sierra 80-grain MatchKings are seated to touch the lands in three different barrel chambers. You need to know the overall length if you want to experiment with this tactic.

dead_length_3_depthsThis tactic is well (very well) proven to promote accuracy. Usually. The overall idea is to introduce a bullet dead straight into the bore. Entry will be smoother. This is also an asset to concentricity, or centeredness. If not touching the lands, scooting a bullet out to be very near the lands helps, usually, and it’s a near-requirement for some bullets. The reason is pretty clear: the shorter distance the bullet has to “jump” before it engages the lands and enters the bore, the less can go wrong. Off-centeredness may then be less a factor over a shorter distance. The bullet is already in-line with the bore, and that overcomes any small alignment imperfections that might exist elsewhere in the round. Gravity also factors in, even in that short gap.

Dead-length seating is not the same as “soft-seating.” You’ll encounter that term. Soft-seating is sizing the case neck inside diameter to just barely less than the bullet diameter, and the idea is to have the bullet “out” and then let contact with the lands finish the seating the bullet into the case neck as the bolt closes. That requires very light case neck “tension” (less than 0.001 difference). Bolt-actions only! This eliminates the effects of any bullet dimensional issues. I’m not recommending this, but there it is. Pressure cautions are increased with this tactic! It’s common for soft-seating to engage into the lands by 0.010-0.020. So now you know…

My experience has been that once it gets past 0.010, more jump doesn’t really make any difference. I see the biggest improvements (if I see them) when it’s reduced to 0.005 or less. That sort of reduction is not often possible when loading to cartridge overall lengths that fit into a box magazine. However, there are some 52-grain-range .224 bullets that have to be seated more deeply than the generally-accepted 2.260-inch mag-length maximum for an AR-15. Hornady’s 52-grain HPBT for one. This bullet will be 0.020 into the lands, or more, at 2.260 inches. There are other similar bullets that will do the same: contact the lands at a cartridge overall length less than the magazine allows.
My experience has been that once it gets past 0.010, more jump doesn’t really make any difference. I see the biggest improvements (if I see them) when it’s reduced to 0.005 or less. That sort of reduction is not often possible when loading to cartridge overall lengths that fit into a box magazine. However, there are some 52-grain-range .224 bullets that have to be seated more deeply than the generally-accepted 2.260-inch mag-length maximum for an AR-15. Hornady’s 52-grain HPBT for one. This bullet will be 0.020 into the lands, or more, at 2.260 inches. There are other similar bullets that will do the same: contact the lands at a cartridge overall length less than the magazine allows.

Generally, the longer and spikier a bullet is (secant-style ogive, high-caliber-radius), the more likely it will be to perform best starting nearer the lands. For good example, although it’s contrary to some others’ experience, I have yet to get good accuracy from any of the true “VLD” (Very Low Drag) bullets until they get on the lands. Same goes with others similar, like the Hornady A-Max; those are more tolerant of jump, but don’t like much of it.

Three things:

One — first, foremost, always — this tactic will raise pressure! There’s nothing to worry about here until the bullet actually gets on the lands. Going from “near” to “on” is a huge difference! The reason is the loss of space for burning gases to occupy, release been delayed because the bullet is working as a plug from the get-go. Reduce any load one full grain! Work it up from there. It might end up being more like a half-grain, but it will at the very least be that much difference. That’s significant.

Two is that approaching dead-length isn’t usually possible on any but single-loaded rounds (not fed from a magazine). This also goes for bolt-actions (and, honestly, I really only recommend this tactic for bolt-guns). Just depends on the space available for the rounds at rest: magazine length. For my ARs I do it only with “long” bullets used for the “slow-fire” portions of a rifle tournament (rounds must be fed singly). (With one exception, shown nearby…)

Three is that it’s going to change. As the rifle throat erodes it advances, distance to the lands gets longer, so what was “touching” some-hundred rounds ago is no longer “touching” now. Certainly, that varies with the cartridge, and will lengthen faster with a .243 Win. than it will with a .308 Win. Get the OAL tool, keep up with it, and it’s easy. However! The load is also changing, a little bit, each time the bullet moves forward, and that can influence velocity and zero.

It’s a lot to keep up with.

Make sure there is adequate bullet retention (diameter difference between bullet diameter and case neck inside diameter, go a good 0.003 inches). Can’t have the bullets jumping forward (inertia-induced). If, for example, you’re loading to give 0.002 hold-off, that little gap can get taken up easily and then, if the bullet gets on the lands, there’s a pressure spike. Goodbye primer!

dead_length_barts

Here’s a couple of purpose-built loads for 100- and 200-yard “reduced” High Power Rifle courses. It’s a .222 Rem. with a chamber built around one bullet: Bart’s 52-grain flat-base. The whole idea was to create an “ideal” round structure where jump could be eliminated entirely. The author had it throated at 0.150 shorter than cartridge overall length that touched the lands at the magazine length limit; 0.150 throat erosion is where the author rebarrels. The author chose .222 Rem. because it’s well more accurate than .223 Rem. There’s also a long case neck, and no donut, ever, to contend with. It’s the most purely accurate AR-15 the author has owned. It’s a solid 1/8-minute-of-angle gun, but its little world of dominance border is 250 yards.
Here’s a couple of purpose-built loads for 100- and 200-yard “reduced” High Power Rifle courses. It’s a .222 Rem. with a chamber built around one bullet: Bart’s 52-grain flat-base. The whole idea was to create an “ideal” round structure where jump could be eliminated entirely. The author had it throated at 0.150 shorter than cartridge overall length that touched the lands at the magazine length limit; 0.150 throat erosion is where the author rebarrels. The author chose .222 Rem. because it’s well more accurate than .223 Rem. There’s also a long case neck, and no donut, ever, to contend with. It’s the most purely accurate AR-15 the author has owned. It’s a solid 1/8-minute-of-angle gun, but its little world of dominance border is 250 yards.
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17 thoughts on “Dead-Length Bullet Seating”

  1. As a general principle, the idea of shortening the “jump” by extending the bullet into the leade until it touches or nearly touches the lands of the rifling, seems dangerous. Instead of accelerating the bullet into the rifling, where it then quickly forms to the lands and moves smoothly and moves on its way (which is the whole purpose of the leade), this article proposes basically letting it build up pressure until that pressure alone, with little or no acceleration, forms the bullet to the rifling. Ever try driving a stake into the ground by merely pushing it with the hammer, instead of pounding it in? The added pressure needed to do this is TREMENDOUS! As a reloader, I would never shorten the leade to almost nothing, but instead I seek to ensure adequate “jump”. A little extra accuracy does not warrant what seems to me quite a dangerous idea.

    1. Shooting is dangerous. Reloading is dangerous. Don’t do anything you are not comfortable doing. But for those with the tools and skill sets to measure everything and ease into it, jamming vs jumping bullets can have a huge payback in competition. Ask any benchrest shooter. Most 30BR guns are set up with zero freebore to START with!
      Another reason NOT to jam bullets for casual use is that when the time comes to eject an unfired round, the bullet will stay in the lands, dumping powder all over your action. So DON’T DO IT unless you need to and can deal with the resulting issues. a .005″ jump is pretty good!

      1. If a gun is designed for zero freebore, such as a BR30, and it has been made specially with the strength to handle that, then that is certainly important to consider — it is a very specific situation. Also, a .005″ jump may be pretty good in a number of guns, although that is only about 1.25 times the thickness of a piece of paper, something that can’t be a little this way or the other for this application. Pounding a stake into the ground with only 1/2″ hammer strokes is a pressure problem as well, to be sure. For those aware of the problem with shooting .556 Nato in a .223 Remington rifle, the biggest issue is that the leade is often not long enough for the bullet to smoothly engage by acceleration, in addition to the secondary issue of there being a higher standard pressure in the .556 round. The solution for generalizing the compatibility was to increase the leade and also to strengthen the gun, basically. My concern is for anyone to take this advice as a good idea for general purposes, when the technical considerations are very important. And heaven help the person who picks up rounds custom lengthened for use in a gun with an eroded barrel or stronger specifications, and puts in in another that cannot withstand that special jolt. The author gave a few basic cautions, which is good, but I didn’t sense what I felt to be a duly serious warning; I got the sense that this was general advice for improving shooting accuracy, and that set off an alarm.

        1. Mr. Bell, the analogy to driving stakes in the ground and forcing bullets into the bore is useless. It is two entirely different games. I have shot bench rest for years and formed brass for various wildcats for years. Line 2 in your missive talks of actions “made specially with the strength to handle that” or line 17 “strengthen the gun” or line 23 “special jolt”. These phrases mean nothing. I also have an alarm set off in reading this comment. You have no idea of what you are talking about. Load to the lands, load single rounds, and watch the pressure and the temperature at the range.

          1. Indeed, if I know not of what I speak, about pressure being higher as a bullet starts closer to the lans, then the author of the article is just as ignorant. He also mentions the pressure differences that this change causes. Thank you, great master, for your “enlightenment”, but you can save the insult for yourself. My comment on this has plenty of backup from various sources. Even you say to watch the pressure at the range. That implies that you recognize the pressure changes as well; or you just like wasting time on useless matters. And I suppose you check pressure by looking at primers, all that formality? Most of us don’t have lab setups for checking pressure, so I can’t imagine how you get accurate readings.

    2. I mostly agree with Mr. Bell. I am not a benchrest shooter but do enjoy handloading (20 years now), & also obtaining tiny groups with my rifles. My methods are to experiment with somewhat different OAL’ s, powders, and crimp or no crimp. However, (and I do believe these processes do make all the difference for my efforts), I use a Hornady Concentricity tool that not only measures the amount out-of-center the bullet is in relation to the case & neck but it also allows me to correct any discrepancies, (down to .002″ or less) both for my handloads and factory rounds. It is not unusual for me to find inconsistencies with factory loads of as much as 20 to 30 thousandts, even in some very expensive premium loads. I also measure each powder charge using a single stage press and I employ other precision habits, like cleaning inside the cases with stainless media, truing primer pockets, and others.

      I might add that I believe a high-pressure concern is the primary reason Weatherby manufacturers their chambers to have very large amounts of leade, in order to prevent a handloader from being able to seat bullets touching the lands while still fiting the cartridges in the magazine. In my Weatherby Mark V in .257 Wby, I cannot seat a bullet out far enough to touch the lands, and still fit the round in the magazine, even using long 120 grain bullets. Instead, I simply use standard OAL’s from the reloading manual to start with along with putting each completed round through my Concentricity tool. I may vary OAL slightly at times, but not to the degree of touching the rifling.

      Having stated all the above, I do also acknowledge there are some handloaders out there who do have the knowledge, expertise, and experience in seating to touch the lands who are probably very successful and still quite safe in their practices; but, it’s just not for me as I can get the degree of precision and accuracy I am happy with (1/2″ or smaller groups at 100 yards), without having to resort to land-touching loads.

      Hope this makes sense to everyone and is helpful information, also. Good Shooting, all!

    1. jump a 300 weatherby bullet and don’t use secant bullets in it unless you are highly skilled reloader. form the brass to the chamber and only neck size. use a concentricity gauge from hornady and straighten the bullet as much as possible. if you really need a secant use a hybrid berger. a 300 win would be easier to make accurate because there is less throat.

    2. Seat the bullet out so it will load into the magazine. Weatherbys have a long leade (throat) This is to handle the pressure better.

  2. I jam bullets into the lands on almost all benchrest guns but jump the hunting guns, No problems here with this type of loading but you inexperienced guys do what makes you happy. There’s more to it than that though but you will learn when you reach that level of reloading experience and shooting .

  3. I would like to get a hornady OAL tool but now I check bullit to the lands two ways.
    First I make a cut in the case neck and close the bolt on the case with bullet
    Second I have a brass rod with two disks with set screws.I send the rod down the barrel and measure to the closed bolt then set the brass disk.Then I put a bullet in the chamber and hold it there and set the rod to the tip of the bullet.The difference is the O CL to the lands.
    But I do get a discrepancy from my two methods.I am trying to seat .15 to .25 off the lands in my hunting rifles
    My .243 Savage does not like the 80 grain GMX or the 95 gr SST but I did get better accuracy buy backing off from .15 to .25 I’m just not comfortable seating any closer

  4. One thing that Mr. Zediker, and many other authors fail, avoid, and/or miss, is the diameter of the leade. If the leade diameter is the same diameter as the bullet (or ever so slightly larger, +0.0002, say), the bullet & bore are automatically aligned, so the bullet-jump is virtually inconsequential to the round’s accuracy, and round-to-round precision. (There is a difference between accuracy & precision.) Pressure influences are still in play with off-land, soft and/or dead-length seating.
    Of course, there will always be variation in the leade diameter, but this can be an important factor when buying a new barrel, and having a custom chamber reamed. High-end, reputable barrel manufacturers start with “perfectly-drilled” blanks, and carefully form/cut the grooves with minute precision. The leade diameter will be the same as the groove diameter when the chamber is reamed correctly.
    Admittedly, this is a “perfect-world” scenario, but it does occur, and does enhance accuracy/precision – regardless of bullet jump – if the full diameter of the bullet is in the leade.

  5. I have very high regard & respect to Glen Zediker’s real-world experience and advice. He is one of my (the) best authorities and authors on the subject of precision reloading.
    One factor that Mr. Zediker, and many other authors avoid and/or miss, is the diameter of the leade. If the leade diameter is the same diameter as the bullet (or ever so slightly larger, +0.0002, say, just to give a number), then the bullet & bore are automatically aligned. The bullet-jump then becomes virtually inconsequential to the round’s accuracy, and round-to-round precision. (There is a difference between accuracy & precision.) Pressure influences are still in play with off-land versus soft and/or dead-length seating.
    Of course, there will always be variation in the leade diameter, but this can be an important factor when buying a new barrel, and having a custom chamber reamed. High-end, reputable barrel manufacturers start with “perfectly-drilled” blanks, and carefully form/cut the grooves with minute precision. The leade diameter will be the same as the groove diameter when the chamber is reamed correctly.
    Admittedly, this is a “perfect-world” scenario, but it does occur, and does enhance accuracy/precision – regardless of bullet jump – as long as the full diameter of the bullet is in the leade.

  6. Interesting subject and one I have interest in. I am a game hunter in CA. and shoot Barnes copper bullets. Per Barnes, I start with .050″ jump” and then vary it to get best accuracy with safe pressure (visible signs/measurements).
    At present, I am shooting a Tikka 7MM-08 Rem, Barnes 140 TSX ,.030 off of the lands. I can normally expect one MOA or a bit better out to 400 Yds. which is my “ethical maximum” deer range from a solid rest.

  7. I started reloading in the mid 60’s but I am not a bench rest or target shooter. Still, I appreciate fine accuracy & am always ready to learn from other folks, regardless of their length of experience. I have had a number of center fire rifles but currently only have two. A .300 Win., which I bought in the 70’s & a SXS .45-70. I have never fired a factory round in either gun. I never load anything to max. rated pressure so I doubt that bullet jump will ever come into the picture in regard to pressure. The .300 shoots great with bullets seated almost touching the lands. I have never fired a jacketed bullet in the .45-70 but I’m getting ready to change that. The cast bullets are seated touching the lands or very close to touching. Most cast bullet literature says a big jump is very bad for accuracy. I don’t think it matters much with cast bullets anyway as they are relatively soft. Maybe not so much with cast bullets, but if you were getting excessive pressure with the .300 mag., I would think you would see some signs of it.

  8. Folks, sorry for my inattention. Been trying to finish the new book. I sincerely hope that I made a clear enough point that experimenting with advancing seating depths toward or into the lands is a SPECIALIZED PRECISE handloading tactic. This article was, as I hope also was made clear, done more to provide some information about a tactic that, no doubt will be encountered after research into “precision” handloading techniques. I really don’t recommend most folks try this… I seat to TOUCH the lands on most of my match loads, those for 600 yards or more. It indeed “works.” Going into the lands, no way!

    Likewise, the reason I talked about my “one trick pony” is as an illustration of how such madness can become pervasive, haha, pervasive enough that, yes, a rifle can be built around a very specific cartridge structure. Also, and I know this was clear: buying into that is an agreement that precludes attempting to use anything else in that rifle. Serious business, but with rewards. And, yes, I got that idea from all those benchresters who are responding to this. It’s pretty common. Most across-the-course .308s have shorter throats than factory guns, and David Tubb follows a “minimum” freebore policy on the 6XC. That’s because there’s a lot of room to move that bullet out, when needed. For what it’s worth, true “match” .22lrs get jammed bullets (something like an Anschütz) and that’s why NEVER to fire “high-velocity” .22 through one of those.

    And the fellow who mentioned the leade diameter factor is dead on as well, and that’s yet another “trick” that can be employed. As with all such, again, you’re buying into something that becomes a really narrow margin.

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