Home Forums Hunting & Shooting Long Range Hunting light vs tight bullet neck tension?

Good day.

My lee collet die does not size the neck on my 338 brass nearly as much as the full length die. There are a few points that worries me and that is: How light is too light? How much tension do you need for the best accuracy? Will I get a different point of impact when the neck tension is much lower than when I full size?

I understand that physically checking point of impact with a particular rifle is the best way to get an answer, but in general what has been found regarding neck tension?

Thanks

Pieter

Pieter,

I just went through this with my .308 and a Lee 3-die set. I experienced the same "difference" in neck tension, though my point of impact remained within 1/2" at 100 yards either way as near as I could tell.

Dave

I honestly don't think neck tension has much impact on pressure, etc., which would be what would impact POI. More important is that it has enough tension to keep it from moving in or out of the case, changing the distance to the lands which will affect pressure and thus POI and accuracy. My thoughts on the subject anyway.

Thanks guys.

The thing is it feels as if the bullets goes into the case very easily on the press. Not that I think it is a valid test but I applied around 16 pounds of pressure on the bullet itself pushing it into the case and there was no movement as I know you can run into some issues when the bullet slides into the case and minimizing case capacity.

Pieter

Measure the neck before you seat with a good caliper, then after you seat the bullet. .002" is what you want.

Neck tension consistency is what you really want. I use a few Lee Collet Dies and I've found that they give good accuracy, and it appears to me that they give consistent neck tension. I also have other type dies, for neck sizing and FL sizing and I have one bushing die. In my experience (and I can only speak for myself) the Redding FL Type S bushing die works great if you turn your necks (just remove the high side) to have consistent neck wall thickness, and if you have the proper bushing.

The collet die did worry me a bit at first, since bullets seated so easily. But the good thing was that the seating effort was the same for all the cases. And, I've not found any rounds that had too little neck tension to hold the bullet firmly.

If your neck tension is too low, you run the risk of bumping the bullet deeper which can cause problems of its own. You can also jump a bullet out but I usually see the opposite. For target shooting I don't think it matters much just that it is uniform.

Not arguing with you, but Redding recommends bushings that are 0.001" smaller than a loaded round for their competition dies. This has worked well for me in my rifles (some tight necked and some factory chambers, so various amount of resizing).

They were recommending 0.002" when I first started buying and using their competition dies. Not sure why they changed it.

Redding Tips

Lee will sell you undersized collets for $5, if you want more tension, buy a .001 and .002 and see how that works.

I use collet dies on most of my rifles and when I buy the die I automatically buy an undersized collet. I have found that up to 7mm .001 undersized is good and my 30's and up I do .002

You can also spin the mandrel in a drill and polish about .001 off with fine grain sandpaper. that is what Lee suggested the first time I tried to order an undersized mandrel.

I like a little more neck tension than the collet dies provide stock, I've had several where I could seat the bullet by hand with the factory provided mandrel.

Yup done that as well. I see the OP is from south africa, so maybe polishing it down himself would be better that ordering from lee.

Always used a measurement of .002" after loaded and have never had problems.

Have seen bullets being pushed further into case from just recoil while riding in the magazine.

Fella was shooting 175 grainers out of a 7STW.

For competition this is OK for hunting it is not.

Pieter, since you mentioned your 338 I am assuming it is not your range gun

For a hunting round I will tolerate .02 but prefer .03, years ago I dumped a load of powder into a blind magazine when un loading the rife. And I have seen bullets move deeper into cases under heavy recoil. I just prefer things to stay put.

Good point I guess I'll start single feeding my 338 at the range.

OK, I remember reading somewhere that no matter how much you sized brass down, if you seat a bullet then pull it, the case neck would only show 0.001" loss in diameter. Meaning that the act of seating a bullet was actually "resizing" the case neck if it was sized smaller than 0.001" under the bullet diameter, and thus the max "bullet tension" is truly only 0.001". I honestly thought this seemed a little low, but...

After brushing up a bit on my physics/materials understanding (over 20yrs since I've had these classes ), I did some calculations based on information I could find on brass properties. Guess what? With a 0.284" bullet and case thickness of 0.015" (avg circumference of 0.93934", and using this as length of a piece of brass for the calculations), I came up with 0.001" as the max stretch of a case neck prior to "plastic deformation" (the point at which permanent deformation takes over from elasticity essentially).

I have some bullets that need to be pulled, so I'll measure the case necks before and after. Maybe a separate experiment with some different brass if I can find the time.

Any materials/physics experts here that can add on to this? Or correct it for that matter?

Seriously, not trying to be a smarta$$, etc., would really like to understand this better without spending a week really digging in to this personally.

If hunting bison...all needed is minute of bison, or elephant...minute of tembo! If on the other hand one is attempting to hit a 3" diameter X ring at 1000 yards....consistent neck tension is highly required!!

I'd like to know how your testing turns out. I've pondered this myself. I've had large differences in neck tension with the same batch of loads and can't help but think it has to introduce some variation. To my mind, if the bullet 'easily' moves out of the case, stops at the land and grooves till pressure builds enough to engage the rifling, the powder chamber is larger and pressure seemingly would drop - at least the pressure curve would be different than a bullet with tight neck tension. 'Tight' neck tension seemingly would seemingly build more pressure under the bullet before it moves out of the case and as it engages the rifling. All conjecture on my part.

I've shot a mix of tight and loose neck tension in the same batch of loads and they always seem to be less accurate. I think its because of the inconsistency between shots.

As an aside, I annealed every case I had over the winter and the differences in neck tension seem to have disappeared.

Closer to .002"

https://www.24hourcampfire.com/ubbth...01045/all/Anyone_use_a_leecollet_neck_di

Interested in any information on "plastic deformation" of the necks. It makes sense cause it validates what I have observed. Is there a reference where I can look up the theory and calculations?

Agreed - don't think any of argue that point! Although saying someone would never argue about something around this place is probably not wise...



My first thought would be the opposite as the engraving of the bullets into the land will require more effort (pressure) if it doesn't have a "running start" at the lands (no momentum), and thus would cause a higher pressure spike than If the bullet is held longer by the brass. But honestly not sure this is where the inconsistent neck tension come into play or not.



Thanks for the info and link! I would have to wonder if you had pins down to ten thousandths of an inch, if it would have been closer to 0.001" or 0.002"???

Also, new/annealed brass will have less elasticity (spring back as used around here) than fired/work hardened brass. So I would say your results are definitely not surprising to me. I wish it was easier to measure with more accuracy.

I'll PM you some links later (on my iPad and had found this stuff while on my computer. Lots of information on the elasticity/plastic deformation stuff, less info on brass properties. And I just left the company I was working for that had "experts" that would be able to give me more info on brass properties, etc. So on my own in this right now. Start a new job Monday, but will be awhile before I know any of the technical gurus there (I am an engineer, but moved from technical to the business/commercial side about 10yrs ago...).