RELOADERS CORNER: Bullet Jump, Three

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In this final installment you’ll learn how to take bullet jump completely out of the equation, but it’s not just that simple… Here’s how to get the results you’re after. Keep reading…

Glen Zediker

There’s one more concept to consider to fully finish the topic of bullet seating depth, and it’s literally on the other end of the equation from discussions on bullet jump.

Last two articles were all about a combination of the evils of jumping bullets and also some ideas on reducing the ill effects, and hopefully to the point of zero measurable group size differences. I also mentioned that there are some bullets that just don’t tolerate jumping.

JLK 105 VLD
Bullets like this tend (a true Davis-drawn VLD) not to shoot well unless they start right on or very near the lands. I sho don’t know for certain, but I really think it has at least some to do with, for want of a better way to describe it, their leverage: it’s a lot of front end ahead of the first point of land diameter. These really long bullets don’t have to tip much to shift alignment relatively more.

For many (many many) years it’s been generally held that starting a bullet touching the lands is the easy ticket to better accuracy. That’s hard to disprove. It’s a tactic very commonly used by Benchrest and Long Range Rifle competitors, and savvy long-shot hunters. Now we’re talking about zero jump. Myself and many others have referred to this bullet seating tactic as “dead-length” seating. To be clear: it’s the cartridge overall length that has the bullet nosecone actually sitting flush against the lands (touching on whichever point along the nose that coincides with land diameter). Some literally take that a step farther and increase contact force such that the bullet is sticking into the lands one or more (sometimes several more) thousandths, actually being engraved by the lands prior to launch.

There are two ways to attain or approach dead-length. One is through careful measurement using something like a Hornady LNL Overall Length Gage. That tool should be paired with a bullet-length comparator, and Hornady has one of those too, as do others.

Measure enough bullets using a bullet-length comparator and you will find length differences in a box of most any brand. A comparator, as has been shown before in my articles (because it’s a very valuable tool to increase handloading precision), provides a more accurate means to measure bullet length. It’s a simple tool: the bullet nosecone fits into the opening on the gage, stopping at a point (determined by tool dimension) along the nosecone. Not all such gages coincide with land diameters because both comparators and land diameters vary from maker to maker. They are all “close” but perfect coincidence doesn’t really matter because a comparator will allow a reading at the same point of diameter regardless. Measuring from the base of a bullet to the bullet tip is inaccurate, and not nearly “good enough” to provide a precise enough measurement to venture into lands-on seating depth experiments. The reason measuring from base to tip isn’t good enough is because, especially in hollowpoint match-style bullets, there are relatively huge variations in the consistencies of the tips. I’ve measured easy 0.020 differences in a box of 100. Can’t make bank on that.

Using the combination of the gage that shows overall cartridge length that has the bullet touching the lands and the comparator to precisely record this length, it can then be reproduced via seating die adjustment.

Hornady LNL gage setHere’s a tool set shown many times in my books and articles this pair or something similar is necessary to negotiate this step in handloading. Check it out HERE and HERE at Midsouth.

If using this method, maintain whatever usual neck sizing dimensions are for your routine loads. There’s no need or benefit from lessening the case neck “tension” (which is the amount, in thousandths of inches, of the difference between resized case neck outside diameter and the resulting diameter after a bullet is seated). If that’s, say, 0.003 then keep it at 0.003.

There’s another, maybe better, method to follow if (and only if) you have a bolt-gun that’s to be fed one round at a time. By that I mean the rounds are not feeding up from a magazine but are being manually inserted into the chamber. That method is to reduce the case neck tension or grip to a level that the bullet is free enough to move within the case neck such that it seats itself when the round is chambered and the bullet makes contact with the lands. That’s awfully light in-neck resistance. It can’t be so light that the bullet falls into the case neck, but light enough that it can be scooted more deeply with little pressure. For a number it’s 0.001, minus, and half of that is workable if the case necks have been outside turned (so they are dead consistent in wall thicknesses and therefore will reliably “take” that little tension, meaning respond consistently to the sizing operation). Need a bushing-style sizing die to get that sort of control over the neck sizing dimension.

This method is often called “soft seating.” It’s, as said, very popular with competitive precision shooters. The bullet, keep in mind, isn’t just touching the lands, it’s actually engaging the lands to whichever degree or distance that resulted from overcoming the resistance from the case neck. If you feel anything more than slight resistance in chambering a round, that’s too much resistance. Chances are that any soft-seated bullet will stick in the barrel so extracting a loaded round will likely result in a big mess (elevate the barrel a little to keep the propellant from dumping into the action). Pushing the lodged bullet back out and looking at it carefully gives a good idea of how much resistance it’s overcoming. If the engraved area is much over 1/16-inch, increase the neck sizing bushing diameter to likewise loosen up the case neck. The amount of engraving has a whopping lot to do with the bullet jacket material (you’ll see more with a J4 than with a Sierra).

If you follow this method, then finish the die-seated bullets “out” 0.005-0.010 inches.

Redding sizing die bushing
It’s necessary to be able to fine-tune neck sizing dimension to experiment with soft-seating. A bushing-style sizing die is best. The bushing might also change for different brands or lots of brass if there are thicker or thinner neck walls. Clearly, outside neck turning is a step toward consistency in this sizing operation.

The reason this method can give the overall best results is because it’s accounting for teeny differences in bullet ogives and it also is adjusting itself for throat erosion. As gone on about in the last couple of articles, a barrel throat is lengthening with each round that passes through. What was touching the lands, or jumping 0.015, even one hundred rounds ago is no longer valid, and it’s totally corrupt five or six hundred rounds later. It’s no longer a precise setting, meaning a precise seating depth, and it has to be checked and reset as the barrel ages.

Again, this is not a casual experiment. The level of control and precision necessary to make it work safely and as expected is a step or three beyond what most reloaders are tooled up to deliver.

Will lands-on seating work for a semi-auto? Yes. But only with adequate bullet grip to retain the bullet firmly in the case neck, and that means the same tension that would be used with any other cartridge architecture, and that means a minimum of 0.003 inches difference between sized and seated outside case neck diameters. I do it often with my across-the-course High Power Rifle race guns. Clearly the “soft-seating” tactic is in no way wisely feasible in a semi-auto.

WARNING!
MOVING A BULLET OUT SO IT TOUCHES THE LANDS WILL (not can) INCREASE LOAD PRESSURE! Even going from 0.001 off to flush on will spike pressure. When the bullet is in full contact it’s acting like a plug. I strongly suggest backing off one full grain (1.0 grain) before firing a bullet touching the lands. Then follow my “rule”: work up 0.2-grains at a time but come off 0.5-grains at a time! If there’s ever any (any) pressure symptom noted, don’t just back of a tenth or two, that’s not enough, not considering all the other little variations and variables that combine to influence the behavior of the next several rounds you’ll fire.

THREE REASONS DEAD-LENGTH SEATING WORKS
ONE: Accounts for and overcomes any minor variations in bullet dimensions.
TWO: Minimizes bullet jacket disruption on entry.
THREE: Virtually eliminates misalignment between bullet and bore.

SIDE NOTE
If you’re one who, as many readers have suggested to me, has found that seating a bullet to touch the lands is the only way they get good groups, consider the above three reasons this seating method works and then interpret. If, and this is more common than we’d like to see, you’ve got a factory bolt-action rifle the chamber is likely to be overly generous in size or a tad amount non-concentric, or both. The case wall consistency and also sizing and seating tooling, or all three, might likewise be sub-par. In other words: lands-on seating is overcoming a few rifle issues, not, in itself, proving it’s the one-way ticket to great groups. Mostly, getting the bullet into the lands essentially straightens out alignment of the whole cartridge sitting in that (maybe) big chamber.

The information in this article is from Glen’s newest book, Top-Grade Ammo, available HERE at Midsouth. Also check HERE for more information about this and other publications from Zediker Publishing.

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9 thoughts on “RELOADERS CORNER: Bullet Jump, Three”

  1. I never got that far into target shooting, I just wanted the best accuracy that I could get with relatively simple methods. I only ever loaded 20 rounds at a time and I sized and deprimed my cases and seated a bullet long enough that the bolt would not close without excess force. I didn’t close the bolt but instead removed the case and bullet, then covered the front of the bullet with a felt tip marker ink. I would then reinsert the case/bullet and close the bolt till I felt resistance. Removed it and looked at it and adjusted the seating die so the bullet set a bit deeper. I did this in fractions of a turn. Then re-inked and checked again. When I could close the bolt with no appreciable force required I’d turn the sizing die another half turn in to seat the bullet and check it one last time. If I got no marks that is where I seated my bullets. The rifle was a sporterized Arisaka re-barreled to .257 roberts and I’d heard they were typically set up with a long jump to the lands. It seemed to work pretty good. The rifle had peep sights and I shot a 2″ 5 round group at 100 yards resting the rifle on my shooting bag. May not sound all that good but it was certainly good enough for deer and other medium game.

  2. Excellent! I was going to post on this very subject of adjustments of the bullet further into throat even as slow creep erosion occurs down road of barrel life.
    But you closed comments while my post was sitting there… waiting for me hit the enter key.

  3. I have done this with my Thompson Center Contender and the 30 Herrett and it has taught me more about how to make a gun more accurate than anything I learned up until that point! Literally!!!!
    It absolutely is the most accurate gun that I own!!!
    Bullets touch at 50 yards! And that’s just off of sand bags, no trigger work, no nothing!! My brother tried to match me with his Rugar Mark V but could not even keep close! I DON’T believe that putting the bullet to the lands and leaving space in the case raises the pressures to the amount that the author claims! As long as there is deficient room in the case it should not be a problem! Considering all the different powders available and the different loads, go back to the basics of developing a round, looking at the signs of over pressure and you will discover things for yourself and DON’T just believe what someone tells you in some article! Find out for yourself! It will be much more rewarding!

  4. I use the method of “soft loading” a bullet, usually 150 grain Hornady ballistic tips for my 7mm. Rem.Mag. then I measure overall cartridge length. Then back off a thousandth or two. Barely fit my magazines. So accurate compared to factory ammo, ANY ammo that’s manufactured. But the 139 grain I load to a medium powder load and Hornadys book recommendations for overall cartridge length, which shoots about .75 to 1.25 at a 100 yards. Which I have produced several hundred rounds for a SHTF senario. Just in case! Thanks again for all the great tips.

  5. I shoot Berger 168 gr. VLD bullets in 308 bolt gun and love the results but I don’t intend to make it a single shot rifle by extending that long bullet into the lands for better accuracy. My 5 shot string at one hundred yards that I could cover with a dime is more then enough to bring home the bacon.

  6. When first starting down the accuracy road, I was told the “ONLY” way to seat bullets was to “JAM” them into the lands. Time and experience proved otherwise, for me.

    Long story short, I learned two main things. Three, if you count there are very few Isaac Newton type ‘laws’ in reloading or shooting, except for the KABOOM ones.

    First, every barrel has its own bullet jump preference, and that goes for any bullet, weight, ogive, or coating and that jumps lasts for the life of the barrel. Strange, but true.

    The bullet jump preference for VLD bullets (.224, .243, .264, & .284), at least in all the barrels I shot, and most of them were after market button or cut customs, preferred a .020″-.025″ jump. Also, strange (according to the common wisdom) but true. I suspect most shooters have never tried that long a bullet jump with VLD’s, and that’s why I’ve never heard of anyone else having the same results.

  7. I have used blue print ink from machine shop, markers and smoked bullet with a flame to determine land contact. Good article!

  8. Tried dead length & soft seat with 222 & 30-06 using tangent ogive heads, found 0.020-0.030 off lands tightened groups in Remington 722, 788, & 700 respectively. Soft seating did help cast head grouping in 30-06 though.

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