what is the average neck tention required ?? and what are the symptons of exessive tension

I am not sure that neck tension is a bad thing, though benchrest shooters would be better qualified to answer that. Neck tension increases bullet pull, similar to a crimp. As long as it is consistent, I don't see any harm.

Reading the benchrest boards most of the times I see .003" of neck tension as the starting point. It seems to be a pattern, .003" of neck tension and .003" of neck clearance to the chamber.

I judge tension a bit differently. If the bullet drops into the case by itself you need more tension. If you can turn the seated bullet with your fingers, same thing but better. As long as you cannot turn the bullet in the case I find it okay. Better that than bullets that are tight being seated which may well incease your chamber pressure. Just one mans opinion. Best wishes.

Cal - Montreal

I like at least .002" on magazine guns, less on single shots if using faster powders. In the main I think it depends a lot on application and type of powder. From what I can discern something around .002 will hold 510 grain paper patch in an 1895 CB gun in .45-70 magazine stuffed full, w/o crimp. Don't take that as a recommendation, just an observation. Generally I don't concern myself with the issue unless accuracy is a high priority.

if one puts a micrometer to a lot of expander buttons he'll find they are about .0015-.002 under bullet diameter and they are retracted under a lot of tension. It just seems to be then that the standard tension amount is preset to the expnader button...and without miking the cases for hole size I'd say thay are about .002-.003....Frankly I've never had a problem with this.

My Lee Neck Sizer for the 6.5x55 gave me 0.0015" neck tension. I didn't think that was enough, and bought an undersized mandrell from Lee that gives 0.003". It makes me feel better, though I can't say performance improved.

I would presume greater neck tension implies the neck brass is worked more and work-hardens sooner.

Jaywalker

If I measure the die and measure the brass comming out and subtract to find the difference, the brass only has about .002" of elastic strain before it goes plastic deformation. So that is the most neck tension you can get. Any more bullet to neck interferance than .002" does not give any more neck tension.

quote:

I would presume greater neck tension implies the neck brass is worked more and work-hardens sooner.

No, quite the opposite. As brass work hardens your neck tension will diminish.

Vapo, the expander ball is indeed less than caliber and that is how NT is created. However you NT does not correlate specifically with the measured difference. Brass springs back unless it is work hardened, so a die used for a .308 caliber may in fact be .0015 smaller yet create another dimension in regards to NT. There are three ways to adjust the number. Either use a different size expander ball, bushing dies w/o an expander ball, and/or turning case necks.

It depends on the recoil of the rifle with me..I want enough tension that recoil does not set the bullets back...also enough that the powder burns enough before the bullet completely leaves the case...

On big bores like the 416 on up, I will turn .001 to .004 off the resizer button, enough so I can seat bullets with out crushing the case in any way but I want that bullet very tight, then I use a case filling powder, and a very light crimp...

In the lighter calibers the resizer button is mostly always correct in good quality dies and its not even worth worrying about. your probably getting overly technical, a common malady among gun nuts...

Actually, before we offer measures for neck tension, perhaps we'd better define what what is meant by the figures.

There are several ways of attempting to control neck tension. One way is to attempt to control inside neck diameter. This is typically done with the size of the expander or collet in a Lee Collet Die.

Then there is the option of controlling outside neck diamater - typically done with a die without expander but known inside neck diameter. Redding and other bushing dies as well as dies honed to a particular neck diameter are typical examples. Although not mandatory, outside neck diameter control is often associated with exact measurements for neck wall thickness - as in neck turning.

On top of all that, how is "neck tension" measured?? Method #1 is to measure the device with which we attempt to control (outside) neck diameter vs. the diameter of loaded brass necks, say. This is the way Redding defines neck tension. It is an easy way to provide a figure, but the figure may not strictly mean the same from brass lot to brass lot.

If you control inside diameter, you'd measure difference between expander (collet) size and bullet diameter. Almost the same method, really, but different measurements.

Another way, is to measure the difference in neck size between sized and loaded brass. In contrast to method #1, this method allows you to take into account the amount of springback in the particular lot of brass you are working with. In that sense, this is really the most accurate measurement for neck tension, although somewhat tedious to use, and therefore less common.

To the 2nd half of the original question:

quote:

what are the symptons of exessive tension

If you really get too much neck tension, you'll start damaging the heel of your bullets when you seat them. Essentially, you are asking your bullet to do the job of an expander. The heel is about the worst place you can damage a bullet in terms of accuracy.

I guess one could make a case for rising pressure with too much neck tension...??? Although this probably only happens (or at least becomes dangerous?) if the case neck can't expand properly to release the bullet (e.g. because the case is too long for the chamber).

- mike

Jaywalker, I had the same problem with my Lee .280 Rem. collet neck resizing die. I chucked the mandrel of the die in a drill and sanded it down till I acheived .0025" of tension (the difference between a resized, unloaded case and a loaded case). For a hunting rifle of this caliber I think this is about right.
Woody

There a number of ways to adjust neck tension. One is to size the neck down to a certain diameter and leave it as is. Springback will then decrease neck tension with every reload.

Another way is to size down, then expand with a mandrel. Springback will then increase neck tension.

I size below bullet diameter, then expant with a mandrel .0005" smaller than bullet diameter. This gives me about .001" of neck tension and my seater does not mess-up my bullet noses.

.003" is excessive and bullet noses take a beating. Your reloads will look like a kid made them.

some very interesting replies,my rilfe a 7mm/300 wsm with a 140 Nosler fail Safe has got 3 thou of tension,being a magum and having a magazine I would have thought it would have been enough ?? or do you think its too much

I recently ran into this problem this last spring in high power competition. I was having trouble with my 600yd groups out of my DCM AR. The problem was that my velocity spread was around 100 fps. This was causing different trajectories at 600 even though at 200yds the load would shot around 1 MOA or better.

After trying everything; brass prep methods, primers, powders, I finally found neck tension to be the culprit. My .223 need at least .003 neck tension to narrow the extreme spread. I was from the school of thought that less neck tension was always better. But, after some research I found that it can help the powder ignite and burn more uniformly because the neck tension holds the bullet in the case a split second longer. It makes since. I was worried that this may have a negative effect on my overall average velocity and pressures, but it didn't. But, seating the bullets out to the lands can definitly have an effect on pressure.

The neck tension theory seems to be more true with stick powders, like Varget, than with ball powders, like AA2520.

But, this didn't entirely fix the problem. In-order to have uniform neck tension you have to have uniform neck wall thickness. So to achieve this I started turning the necks just so that they would clean up. Then I would anneal them. This is what brought my extreme spreads from 20-30fps to 15fps or less. Even though my 200yd groups seemed to open up my 600yd groups shrunk drastically, to 1 MOA.

I have found Winchester and Remington brass to vary a .001 or more in wall thickness. This can cause one loaded round to have a neck tension of .002 and the next a neck tension of .004. Without a doubt though, neck tension is the most overlooked factor when it comes to reloading.

When it comes to hunting, I rather use neck tension than a crimp, if there is not cannelure on the bullet, to hold it firmly in place.

I'd like to add that even if you BR prep your brass, neck tension will still vary due to differecnes in brass alloy between cases. Some will have hard necks no matter how much you anneal. I got to the point where I shot my rounds and sorted cases based on where they would print.

One good way to lower ES is to use the fastest powder for your application. For HP, VV N-130 is best for short range and 135 is best for long range heavy bullets. That is the only way to keep ES low.

quote:

Originally posted by Foxshooter:
some very interesting replies,my rilfe a 7mm/300 wsm with a 140 Nosler fail Safe has got 3 thou of tension,being a magum and having a magazine I would have thought it would have been enough ?? or do you think its too much

How do you control and measure your reported neck tension?? Make the effort of measuring a few sized vs. loaded neck diameters. As mentioned above, this is actually the most telling way of measuring, as it takes the brass springback into account.

Normally, .003 (even measured as difference in bushing size vs. loaded round neck diameter) is a fair amount of neck tension. As James noted in his last post, essentially the more neck tension you build into your rounds, the easier it is to overcome differences in brass. Sadly, there is a limit to how far down this road you can go, and expect improved results. Only testing will tell. In addition, if you use bushing-type dies, the smaller the bushing you use, the larger the chance your sizing will produce runout. So again, there is a limit to what is achievable.

In your particular case, and since you are asking about a hunting-type (as opposed to competition oriented) cartridge, this is what I'd look at in turn to establish a sensible level of neck tension:
1) do you clearly feel the neck tension when you seat the bullets, and does it feel "the same" from case to case?
2) on your loaded rounds, can you move the bullets when you press the tip of a bullet against the edge of your reloading bench??
3) do the bullets move under recoil?? Fill your magazine, shoot all but the last (or two last), and measure OACL before and after firing.

If all of the above seem OK, I would probably think you are fine with neck tension where you are.

One of the problems with neck tension - although probably more in competition type applications, as James and Ralph mentioned above - is that it is sometimes difficult to pin down differences in this parameter. James used velocities as an indicator, I mentioned "feel of bullet seating" above as another (inadequate) indicator. There is at least a third, perhaps more direct way of detecting varying neck tension. Sadly it costs $$$ and time and is not applicable to all cartridges. K&M builds an arbor press which allows a strain gauge to be employed to measure the force needed to seat bullets. That way, you get an immediate and quantified feedback on how much your neck tension varies. Needless to say, arbor presses only work with in-line dies, so for all us "screw-in" types, this is not a solution. But the option exists...

- mike