Neck tension vs seating depth
- Thread starter SDDasher
- Start date
Brians356
Silver $$ Contributor
FWIW:
Virgil King, who owned the fabled "Houston Warehouse" and established new standards for bolt rifle accuracy (indoors anyway) said "both". He seated bullets to engage the rifling so that the lands made a witness mark on the bullets 1/2 the width of the lands.
And his neck tension control was unprecedented (all this from memory - article available online):
After reaming and outside turning the necks to fit the extremely tight chamber neck, King then seated the bullets in fired (unsized) cases with a Wilson die using only hand pressure (no arbor press) and opined it was about 15 lbs of force. (The parent cases were fabled Sako 220 Russian - now long out of production.)
Using feel only, if seating resistance varied from what he expected, he either discarded the case (if it was too light) or "reamed" the inside of the neck slightly w/ 3 turns over a roll of 400-grit sandpaper (if it was too tight.) Then he fired the case again in his tight-neck chamber and tested it again.
In the end he finished up with cases so consistent, he could feel the bullets subtly "click" home into the slight groove the flat-based bullets' heels left in the fired necks. If a bullet didn't click home, he discarded the case, otherwise the seating depth was perfect - he never even measured the loaded rounds to verify lengths!
Using these extreme methods, he was able to shoot 0.070" (or smaller) groups at 100 yards consistently (again, indoors) with both 22 PPC and 6 PPC. (He said the 22 was better overall than the 6 in The Warehouse.)
So, the lesson I take is that neck tension does matter, maybe even as much as seating depth, but for the level of accuracy the average shooter seeks, and can reasonably obtain, consistent seating to whatever depth you finds works best is probably more important, and certainly easier to control.
Virgil King, who owned the fabled "Houston Warehouse" and established new standards for bolt rifle accuracy (indoors anyway) said "both". He seated bullets to engage the rifling so that the lands made a witness mark on the bullets 1/2 the width of the lands.
And his neck tension control was unprecedented (all this from memory - article available online):
After reaming and outside turning the necks to fit the extremely tight chamber neck, King then seated the bullets in fired (unsized) cases with a Wilson die using only hand pressure (no arbor press) and opined it was about 15 lbs of force. (The parent cases were fabled Sako 220 Russian - now long out of production.)
Using feel only, if seating resistance varied from what he expected, he either discarded the case (if it was too light) or "reamed" the inside of the neck slightly w/ 3 turns over a roll of 400-grit sandpaper (if it was too tight.) Then he fired the case again in his tight-neck chamber and tested it again.
In the end he finished up with cases so consistent, he could feel the bullets subtly "click" home into the slight groove the flat-based bullets' heels left in the fired necks. If a bullet didn't click home, he discarded the case, otherwise the seating depth was perfect - he never even measured the loaded rounds to verify lengths!
Using these extreme methods, he was able to shoot 0.070" (or smaller) groups at 100 yards consistently (again, indoors) with both 22 PPC and 6 PPC. (He said the 22 was better overall than the 6 in The Warehouse.)
So, the lesson I take is that neck tension does matter, maybe even as much as seating depth, but for the level of accuracy the average shooter seeks, and can reasonably obtain, consistent seating to whatever depth you finds works best is probably more important, and certainly easier to control.
my pseudoscientific observations: seating depth stays THE SAME after the bullet is seated...even for years, and years, and years. neck tension, however, CHANGES from the millisec the seating die does it's thing. neck tension is high, then the brass starts to relax as the bullet continues to try to expand, then reaches a point where compression of the brass equals the expansion of the bullet. fine, if everything stopped at this point, but it doesn't seem to happen..."cold bonding" sets in and can result in the highest "tension" or grip on the bullet. i have shot these loads at different times in this senario and early on the group is very small, but later the group changes, usually for the worst. these events commonly happen when bullets are jumped but not so when bullets are jammed. my guess is that a jammed bullet requires MANY times more pressure to move than the pressure to break the neck tension of a jumped bullet. i have jammed loads over a year old that shoot to the same point as on day one, but cannot get jumped one to do the same. my motto: a small group jumped load...shoot soon, if jammed...shoot whenever.
Proper and regular annealing... very important
Size to give 1.5thou neck tension... bit more bit less, doesn't matter, be consistent.. .see above
Seating depth.. just off lands... Nothing cast in stone. I must be able to extract loaded rd so no hard jams.
Work up all loads weighing charges very precisely. Do it consistently. Track affect at 600m of small powder charges.
Outside neck turn EVERY firing. Anneal every 1 to 2 firings... do it properly. Trim as needed.
With good bullets, barrels, powder/primers, optics, stock, trigger, bipod and shooter, I get accuracy that I feel is as good as all of the above can shoot in an F TR class rifle....
Most important part still learning... How to read that wind...
Jerry
PS K&M and other makes tools to measure seating pressures.
the possible reason the jammed bullets work whenever, that cold fusion is broken when the bullet is jammed into the rifling.
Size to give 1.5thou neck tension... bit more bit less, doesn't matter, be consistent.. .see above
Seating depth.. just off lands... Nothing cast in stone. I must be able to extract loaded rd so no hard jams.
Work up all loads weighing charges very precisely. Do it consistently. Track affect at 600m of small powder charges.
Outside neck turn EVERY firing. Anneal every 1 to 2 firings... do it properly. Trim as needed.
With good bullets, barrels, powder/primers, optics, stock, trigger, bipod and shooter, I get accuracy that I feel is as good as all of the above can shoot in an F TR class rifle....
Most important part still learning... How to read that wind...
Jerry
PS K&M and other makes tools to measure seating pressures.
the possible reason the jammed bullets work whenever, that cold fusion is broken when the bullet is jammed into the rifling.
Brians356
Silver $$ Contributor
Chaps,
Very good comments and theories! I am all ears - not a competitor, so cannot question your approaches, but I do have a few comments.
Re: "cold fusion" (which may be from Galvanic corrosion, or what is called "stiction") - I have no doubt it plays a role, especially when rounds are stored for years. What pops into my mind (since I have used it a lot) is moly coating. Seems like moly would tend to mitigate any potential bonding, whatever the process in play.
Re: Brass relaxation - From what I glean the brass does relax over time. But in the specific example I cited (where the necks are never sized, but the brass rebounds in the extremely tight chamber back to ready-to-seat dimension) it wouldn't be an issue. Mr King was seating bullets by hand, and feeling for the heel clicking into place. His whole approach to necks and seating seemed designed to produce relaxed brass and absolutely repeatable neck tension. When he felt a bullet seat by hand with either too little or too much tension, he simply discarded that case.
Re: Bullet jamming mitigating neck tension variation (or stiction): Seems plausible. However, I am not so sure the neck doesn't expand and release the bullet almost immediately, before the bullet has a chance to move forward much at all. I've read different slants about this. Can someone cite an article or study on it?
Very good comments and theories! I am all ears - not a competitor, so cannot question your approaches, but I do have a few comments.
Re: "cold fusion" (which may be from Galvanic corrosion, or what is called "stiction") - I have no doubt it plays a role, especially when rounds are stored for years. What pops into my mind (since I have used it a lot) is moly coating. Seems like moly would tend to mitigate any potential bonding, whatever the process in play.
Re: Brass relaxation - From what I glean the brass does relax over time. But in the specific example I cited (where the necks are never sized, but the brass rebounds in the extremely tight chamber back to ready-to-seat dimension) it wouldn't be an issue. Mr King was seating bullets by hand, and feeling for the heel clicking into place. His whole approach to necks and seating seemed designed to produce relaxed brass and absolutely repeatable neck tension. When he felt a bullet seat by hand with either too little or too much tension, he simply discarded that case.
Re: Bullet jamming mitigating neck tension variation (or stiction): Seems plausible. However, I am not so sure the neck doesn't expand and release the bullet almost immediately, before the bullet has a chance to move forward much at all. I've read different slants about this. Can someone cite an article or study on it?
I have read theories on here about the issue of "cold fusion" but do not or cannot cite any articles. Shooting as often as we do in the South, that usually is not a concern of "F'ers" I know.
I am now contemplating how much tension is necessary on the bullet to create significant pressure increases. I notice my soft seated bullets shoot about the same velocities as the ones just off the lands and beyond.
I am now contemplating how much tension is necessary on the bullet to create significant pressure increases. I notice my soft seated bullets shoot about the same velocities as the ones just off the lands and beyond.
how about the 333 method... (Edited)
.003 neck tension on bullet
.003 neck clearance for case expansion in fired chamber
.003 seated depth into lands
Since you have to start somewhere when working up a load...
I would think that this would be a great starting point for developing a solid shooter.
.003 neck tension on bullet
.003 neck clearance for case expansion in fired chamber
.003 seated depth into lands
Since you have to start somewhere when working up a load...
I would think that this would be a great starting point for developing a solid shooter.
and THEN..... you had better start with the Eric 100 yd load work-up system in order to at least START to find the best 3 groups that are side by side... not just one group... but the BEST 3 next to each other... and then after choosing the middle group of the BEST powder charge... then start all over again trying to find the BEST SEATING DEPTH.
Without a system... it's just winging it without a prayer....
Without a system... it's just winging it without a prayer....
Oops.... LOL.... Did you mean .003 (3 thousands)..... this one....LOL.
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