Home Forums Hunting & Shooting Ask The Gunwriters How much "neck tension?"

I see more and more guys talking about how much neck tension they're setting up by various means. "I got .004" neck tension."

My take: if I understand the purpose of annealing case necks, this is a bunch of hooey. Tension is not a linear measurement to begin with (but I see the need to try to quantify somehow), and if you do not take the condition of each piece of brass into account (and just how would you quantify or qualify that in itself??) your linear measurement is pretty meaningless and real neck tension might be anything at all.

Your take?

All my brass that I measure for neck tension is consistent.

Same wall thickness all the way around. Resize the OD to .001" smaller (BUSHING DIES) than a loaded round goes. That is my "neck tension."

I read an article in Handloader magazine yrs back by Gary Sitton about loading ammunition for the PALMA match. The yr of that article the manufacturing of the ammunition was awarded to Jensen's Custom Ammunition. In the article it tells how the special run Winchester 308 cases were prepped and gave the accompanying measurements including neck tension. With a sample number of cases sized the OD measurement was .338". The necks were then expanded with a .3075" plug eased into the neck to a depth of .2". The result was approximately 60lbs of seating tension. He said would have liked a lot less but because of how the ammo would be handled a heavier grip on the bullet was used. He does not say how the neck tension value was acquired . I can only guess that he some how had a gauge set up at the time of seating the bullet.

To the best of my ? memory ? ( take that for what it's worth ), I began handloading in 1975.
So that's 42yrs. I don't shoot comp. just the best I can get for hunting accuracy.

I ain't got the 'least' idea what my neck tension is, measures, compresses , whatever.

IMO unless you're comp shooting, I wouldn't worry about it.

Y'all can flame away ALL you want, it won't change anything.

Jerry

I agree with what you say and have no idea how you could quantify. When firing, pressure varies with each shot, so wouldn't hardening of the brass vary also? When annealing, you have no way of knowing how softened each individual case neck would be.

Using Pahntr's method, the inside neck diameter would be the same and might give equal tension but there's no way of knowing how much tension that is or even if it's consistent.

Perhaps finding a way to measure how much pressure it takes to seat a projectile would give some idea of neck tension.

Well heck, while I spent 30 minutes writing this, EZEARL was already posting what I was trying to say.

I don't think there's really any way to measure tension so what guys default to doing is measuring the necks before and after and using that value for "tension". It's not really a measure of tension of course, but it's all we can reasonably measure and the thought process is that given consistent brass properties the tension will be the same between cases of equal sized neck diameter. This changes with firing as the brass is hardened so annealing is used to return the brass properties to as close to new as possible.

There are products like the 21st century hydro press that measure seating force which gives you a closer approximation of tension, but it's still not an actual measurement of tension. I think you could infer that rounds requiring the same seating force would have similar neck tension, but it's still not a direct measurement.

http://www.xxicsi.com/hydro-bullet-seater.html

Looking for consistency, the least tension to hold the bullet in all circumstances, provides the most consistency. Single firing, as in benchrest or at the range, tension provided by .001" difference was always my most accurate measure. Increase the tension and groups progressively got larger. Finding the happy medium for a hunting rifle where you might require a second or even third shoot, you had to have enough tension to hold bullets in cartridges in the magazine from setting back upon recoil. The most accurate off the bench was not necessarily the best for a hunt. I always used a difference of .002" for the benefit of accuracy, with the hope I wouldn't require a second shot. Take a note from the old benchresters. They used zero tension and allowed chambering to seat the bullet.

Makes sense to me. One possible contributor is that less neck tension makes for less runout. When I'm using a bushing die, I try to find the bushing size that holds the bullet but allows me to move the bullet with finger pressure only. That's not zero, but close. Then drop down two thousandths.

That's not really a measure of tension, but it's as close I can can get and as close as I need.

Yep, and if the necks are turned to an even thickness, annealed regularly, and sized consistently, neck tension will be very consistent. Or should be, if the bullets are of consistent diameter.

It seems that there is mostly general agreement with what I've said, so now I want to take it a step further.

If the benchrest fellows are using equipment like the 21st Century Hydro Press, then it must be useful because the force required for seating tells the story of neck tension.

I've often heard (read) the argument that you can pull the bullet of a loaded round, and if the I.D. of the neck is the same as it was before seating that bullet initially then nothing needs to be done to the neck before re-seating the bullet. Anytime I have needed to pull a bullet to make some kind of change, I have had to resize the neck in order to get the correct seating effort---based strictly on "feel," of course. Re-seating the bullet without resizing the neck has always resulted in very light force required to send the bullet back home in the case neck (which is not a bad thing in itself, but it makes that one single round different from the rest). So, I would hypothesize that the change in inside neck diameter is too small to measure but still causes an easily perceptible change in force required to re-seat. I can think of no other possibilities. What else could it be?

A disturbance in the force.

LOL. Your guess is as good as mine!

my take ? it's something "new" to post about on the various forums now that the other terms
such as SD and the like are now commonplace for posts. somewhere in the mix, north american
game animals got real hard to kill, and must be shot at 500 yards with the proper SD bullet out of
a case that's been through an annealing machine, all the while properly twisting the target turrets
of a $3000.00 scope after consulting the chart taped to the rifle stock, etc. etc.

That's right. We should all be using longbows and wooden arrows.

I use gauge pins to measure the inside of my case neck and shoot for .003" under the bullet diameter. Having a selection of neck bushings allows me to control that dimension.

Brian Litz did some testing in his second book and determined that .003" of "tension" resulted in the lowest standard deviations which was good news for me since that's what I was already doing.

I've found that anything over .002 gets you more resistance in seating bullets. Once the bullet has been pushed into the neck the seating tension is lighter. Pull the bullet and measure and you'll see that the bullet has resized the brass and you have .001-0015 neck tension. I use bushing or collet dies set to give .002 tension to minimize work hardening the brass.

And the goal of controling neck tension is? Seventeen posts and not one mention of what advantage is to be gained. Are group sizes significantly improved? I can't imagine much is to be gained in a hunting rifle.

GW, I'm with you on this. PT Barnum said " There is a sucker born every day and none die". The truth of the mater. Is, as with custom guns, three thousand dollar scopes, and all the rest of the bull chit. All though it impresses the new suckers. Ninety seven percent are incapable of chooting the difference any or these fools errands may accomplish. I guess my advice to chooters. Would be if ya can't hit a bull in the arse with a shovel. Spending ten thousand dollars, and chasing witch hunts like this topic. Is going to get ya the same result. ( Still can't hit a bull in the arse with a shovel ) So although every body gets a trophy. All the money, and scape goat hunting. Will not correct the problems with in. Take care of the shooting problem, and the other chit will be far less expensive! JMO




Take care, Willie

In the article I reference to in my post by Gary Sitton. "The result was approximately 60lbs of seating tension. He (Bob Jensen) said (in the interest of accuracy) he would have liked a lot less but because of how the ammo would be handled a heavier grip on the bullet was used."

SORRY. I should have included what I have in parenthesis above in my first post. Evidently Bob had done enough research into how neck tension affects accuracy that he found it important enough to mention it in the article.