NNeck Tension

[swadiver]

so................ i use a Lee Collet die on my 6BR's necks for sizing. i have gotten excellent results but am always looking for ways to improve on things.

I have never messed with using an undersized mandrel for some additional neck tension, the standard mandrel gives about a thousands of neck tension. i ordered Lee's mandrel that give an additional thousand of tension

so, are results for variation in neck tension bullet specific? chamber specific? load specific?
what is the best experimental way to proceed with these changes?

thanks

 

[brantfredrickson]

I loaded about 5000 rounds with Lee Collet die with an undersize mandrel and also got excellent results. The undersize mandrel felt more consitent when seating the bullets. I haven't done this with a regular size mandrel versus an undersize mandrel, but shoot 25 shots each of your developed load over a chronograph and see what the difference in SD/ES are. I did do this with the Lee Collet die and a neck turning mandrel die used to size the necks. And the results, only a couple of points SD, said to move from the Lee Collet die to the neck turning mandrel die which I did. Since you will have already bought the hardware, it is an easy move to make.

 

[Shynloco]

.....so, are results for variation in neck tension bullet specific? chamber specific? load specific?.....

IMHO, something I discovered over the years and especially once I got into Benchrest Shooting and "Precision Reloading", was that there just some INHERENTLY forgiving and easier calibers to reload for. And then there are some that test my patience, even to the point of saying, ENOUGH ALREADY! Time to try another caliber. Some of those more "forgiving" calibers I've encountered, are also the same calibers that give me the most accurate and best results downrange on paper. Those include the 6br (Norma), and the 30BR (to name a few). And both come from the same sized casing.

Now more specifically to what swadiver was referring to, I believe regardless of the method you use (I do not use a Lee Collet Die) there are certain factors that effect neck tension. And adhering to a couple specific reloading practice,s helps maintain that consistent neck tension. For instance, I begin by taking virgin Lapua 6br(Norma) brass and fireforming it before doing anything else to it. Having fired it once and without resizing it in any way, I SLIGHTLY turn the brass (on a 21st Century Turning Lathe) to eliminate any uneven (high or low) spots to get me the best concentricity possible. And remember, if you take too much off, you may be increasing the clearance between the brass and the chamber walls (in a custom chamber -vdesired is .002). I then FL resize my pieces of a brass (in a group of 40 pcs since I don't compete) using a Redding FL "S" (Bushing) Die. I re-check Concentricity and find the needle barely, if at all (less than .001) moves using a 21st Century Concentricity Guage. I then load my proven load and go shoot. After that, I do the same thing over and over again with one exception. I ANNEAL my brass every third shooting. And to swadiver, I've found that ANNEALING helps greatly in eliminating that neck tension variation.

Now I will say, that I do not use the aforementioned procedure when it comes to reloading for either my .308 or .260 Remington in which I use a specific oversized mandrel (as the final step in resizing) which gives me the neck sizing I need, plus a better concentricity in the necks than does my Redding FL "S" (Bushing Die) that I do the FL resizing for the brass. SO the mandrel sizing comes AFTER I FL resize in the "S" Die.

SO I guess whatever method you employ and gives you the best results you seek, is what you should stick with. But remember to keep the brass as fresh and resilient by ANNEALING. And find the equipment and procedure that works best in your particular rifle and reloading regiment.

Alex

 

[swadiver]

The problem with using the LCD is that at some point you will need to full size your brass because it wont fit in your chamber. Here my response to a previous post on neck tension.

Some of us know that, of the 3 components of the Holy Trinity of precision ammo (powder, seating depth and neck tension), neck tension is the most difficult to control.

I know that everyone likes to control neck tension with bushings but to me that doesn't seem like a very good way. From my way of thinking bushings transfer any variance in neck thickness to the inside of the neck where they have a direct impact on neck tension. That is not a good thing, because no matter how careful you are turning necks there will be variances, and those variances will impact neck tension.

I believe that the outside of the neck has minimal importance, as long as there is a minimum .003 neck clearance for bullet release. The only important thing is how thick the necks are because that has an influence on spring-back. IMO the part of the neck everyone should be focusing on is the inside of the neck, or more appropriately inside diameter. The inside diameter is what influences neck tension, if one can transfer neck wall variances to the outside of the case it is that much better.

So the question is: How do we control neck tension from the inside of the neck? What if instead of honing die necks (an irreversible and often problematic process because dies are hardened, not to mention that you have to be twice as accurate with a die then with a mandrel, an impossible taskfor most small machine shops) we were to use a mandrel to expand the necks to provide the desired neck tension? What would a mandrel do?

Well, ... a mandrel would control the inside diameter of a case neck much more precisely than any bushing ever can. It could also transfer neck thickness variances to the outside of the neck where it doesn't interfere with neck tension and bullet release. That's good isn't it?

I have been using mandrels for thousands of cases. The problem is that just when I have a mandrel that gives ideal neck tension (down to .0001 precision) it starts to wear, and after a couple of thousand cases it is done. Making another mandrel to .0001 precision is very difficult/not possible for most machine shops and grinding shops. So I set out to look for a solution. I eventually focused on the Hornady bullet puller collet, because that's what I had. I started using the bullet puller to hold pin gages to expand the necks to match the turner mandrel.

However, the bullet puller did not hold the pin gages as co-axially straight as I wanted, so I approached Kenny Porter ( kennethp@portersprecisionproducts.com ), who makes all kinds of things including parts for pacemakers (can you think of anything more critical?). I told him I wanted him to make a die for me that would hold a pin gage, actually a range of pin gages ie .305, .306, .307, .308 and .309. Once I showed him what I had in mind he made a leap to a collet that is ideally suited for what I wanted. The collet holds the cutting bit for a CNC machine. It has real holding power. Here’ the mandrel die that Kenny Porter made for me.

Pin gages are small tubes 2" long and can be bought for a few dollars and they are available in dimensions as exact as .0001 (+/- .00002). They generally have a 60 to 62 Rockwell hardness, like tool steel. They are ideal for this purpose, all you have to do is bevel the tip. To bevel the tip all I do is chuck the mandrel in a drill and spin it against a grinding stone until I get the tip that I desire. Takes less than 5 minutes.


Now, when I need a new mandrel I buy a Vermont Gage pin gauge. If you’re looking for +/- .0002 precision they are round $3 each. If you really want to get precise and have a mandrel to .0001 (+/- .00002) precision then the price jumps to around $18 and you’ll have to order directly from Vermont Gage. For $18 you get a mandrel and a certificate of accuracy and the name of the guy that inspected and when.

This mandrel die makes all other mandrel die I have seen or bought look primitive.

Good luck,

Joe

looks great, can I get the die that was made for you as well?

btw, I use a Redding body each firing as well to size the rest of the case.

 

[Willie]

Contact Kenny at his address posted above. Joe put me on to his die this past summer and it has proven to be a great investment. Kenny is a very nice guy to deal with and will answer all your questions.

 

[swadiver]

Contact Kenny at his address posted above. Joe put me on to his die this past summer and it has proven to be a great investment. Kenny is a very nice guy to deal with and will answer all your questions.

Thanks and thanks to all for the input

 

[mikecr]

Interference fit is set with bushing size or LCD mandrel size.
Anything over 1thou after spring back is just excessive sizing, re-expanded by seating bullet, so you're best to set interference at ~1thou under cal(after spring back).

Normal tension is neck spring back(<~1thou) against seated bullet bearing.
Bushing dies allow adjustment of neck sizing LENGTH(area gripped).
So if you want the ability to adjust TENSION, go bushing and separate mandrel expansion.

That's normal tension. If you need extreme tension(like for an underbore), then neck sizing length beyond seated bearing is in order(FL sizing). But you better be running extreme pressure loads to overcome the tension variance in this path. Or, you can develop with constant annealing in your plan. Otherwise this can hurt your results.
There is no reason to do this for a hunting capacity cartridge.

Folks like the low runout in LCD use, but neck tension, the right tension, is far more important to performance.
Add to this, if you're any good at reloading, you can produce ammo just as straight using bushings/separate mandrel.

 

[Richard Coody]

want to have controlled consistent neck tension.

start with quality brass. i prefer lapua.

neck turn to a consistent neck thickness

anneal often and consistently

leave the carbon in your necks

use a quality full length resizing die. custom is best but there are alternatives

finish up with a neck sizing mandrel for final fit. K & M makes a nice kit.

to verify that your neck tension is consistent use a K & M or 21st century arbor press with seating force indicator

 

[fguffey]

And then there is bullet hold, I want all the bullet hold I can get, a good number is 40 pounds. As it has become obvious, it is possible to talk something to death but when measuring the ability of the neck to hold the bullet there are no tension gages, bullet hold can measured in pounds. again, I have tension gages. all of my tension gages measure pounds.

F. Guffey

 

[spife7980]

And then there is bullet hold, I want all the bullet hold I can get, a good number is 40 pounds. As it has become obvious, it is possible to talk something to death but when measuring the ability of the neck to hold the bullet there are no tension gages, bullet hold can measured in pounds. again, I have tension gages. all of my tension gages measure pounds.

F. Guffey

Thats because tension isnt a unit of measure. I cant measure my tension in bananas or good will either. Pounds are a measure of force, ie the tension imparted on the bullet by the case. For some one who knows it all you have an awfully limited understanding of basic physical concepts.

 

[Richard Coody]

guffey talks in riddles only he understands. it is for his own entertainment. it is a waste of time to even rebut one of his statements.

all the bullet hold he can get?

so why do so many competitive shooters use very light neck tension tension?

could be those WWII 06's with those oversized chambers that guffey is so proud of don't really care what the neck tension is.

if you want all you can get try a crimping die.