Case neck tension

[cw308]

What is the best neck tension for accuracy. My measurements on the case necks are. Fired neck OD .341, sized OD with expander ball.334, with expander ball removed 331, with bullet .338. What full length sizing die would you recommend. 308 caliber.

[Longshot4]

Neck tension as I understand it is the amount of tension on the bull it fron the case neck. For best posable accuracy all the case necks should have the same or close to the same tension holding the bullet. Dies like the Redding Type S bushing dies require from 1-2 thousandths. (.001 to .002)". If you Take a loaded case with bullet seated and with a caliper measure the outside of the case neck. Subtract .002" from your measurement of case neck and you will have the correct bushing size. What purpose would you be loading the 338 for?

[4runnerman]

2 thousands tension is perfect

[243winxb]

.002" Redding type S full length sizing bushing die and a .335 bushing.

[F. Guffey]

neck tension? I have bullet hold, I can measure bullet hold in pounds, I can not measure tension because I can not convert tensions to pounds, I have tension gages, my tension gages convert deviation to pounds. I also have strain gages.

Then there is interference fit. I have fitted pieces with 100 ton presses. I have fitted pieces with sledge hammers, interference fit is interference fit, there is no conversion from interference fit to tensions. Something like 3 neck tensions or 4 neck tensions and 1 neck tension equals 10 pounds?

F. Guffey

[F. Guffey]

Because? The interference fit changes the ability of the neck to hold the bullet. Because the neck changes as it is work hardens, a reloader can talk it to death but never catch up with it. I do bullet hold in pounds, a few are coming aground to 'grip'.

Grip to me is a little awkward, 30 grips, 35 grips.

F. Guffey

[4runnerman]

Guffy-- You are a very knowlegable person I can tell from your posts.
But-You always seem to run on the other side of the fence from everyone else.
What you say about neck Tension( I have no doubt is true ). But the whole world ( other than you ) goes by 2 thousands neck tension or 3 thousands,ect ect

[F. Guffey]

4runnerman, thank you, cw308 asked a question, if he is looking for answers he needs all the information he can get. If my responses start sounding like your responses I have become a 'yes man'.

http://tumblr.austinkleon.com/post/9262228034

F. Guffey

[cw308]

F.Guffey, thats alittle bit to deep for me, a neck size with OD of .338 with a bullet, and .334 without a bullet, is .004 to much grip on the bullet.

[243winxb]

is .004 to much grip on the bullet.

NO, its safe to shoot. If shooting an auto loader, that much may be needed. The 223 rem has about 35-40 lbs bullet pull with .002" after the bullet is seated. Over working the neck area may not be good for accuracy. Check the sized neck diameter without an expander. Photo from another reloaders testing.

[603Country]

You want consistent neck tension, and the .002 is a decent number for it. And to translate from Guffey to English, what he's saying is that as the cases get shot again and again, the brass will work harden. Case neck tension might therefore be a little tougher to keep consistent. Annealing can help with that.

I seem to get best accuracy in my 223 and 260 when I use Lee Collet Dies, and neck tension from those dies will be (in my view) rather light but quite consistent. With the 220 and 270 I get great consistency and accuracy with Redding Neck Dies (non-bushing type). Perhaps the fact that I neck turn any cases that aren't Lapua, Nosler, or Norma might help with the accuracy.

[cw308]

243winxb, the neck OD without expander ball .331

[Metal god]

If the neck is sized way small it's my understanding when you seat the bullet . The bullet and the seating process will resize the neck/mouth .

Couple things to think about when using Bushing dies . The thickness of the neck wall matters . If your loaded neck size is .338 . that means your neck wall is .015 . In that case you want the 336 bushing . Now if in that same lot of brass you have cases with neck wall thickness of .0135 that wound mean your loaded diameter .335 and you need a .333 bushing to have the same hold as the other .338 cartridge . Well that is if all the brass has the same ( not sure what it's called ) springiness . For real consistent bullet hold you want the neck wall to be the same thickness all the way around when using a bushing die . I have some cases that have as much as .003 difference from one side of the neck wall to the other . I think those need to be turned so the wall thickness will be the same all the way around .

Now there's always the Lee collet neck sizing die that sizes to the inside of the neck by use of a mandrel . That should give you consistent bullet hold regardless of neck wall thickness but I've heard they don't or can't center the neck over/to the case body . Many people love them , I personally broke mine trying to understand how it worked

I hope this confus er um , helps

[603Country]

If you get a bushing die, be sure to get a good range of bushing sizes so you can select the right size for the cases on hand that might have thin necks or thick necks.

As for the Lee Collet Die, it took a bit for me to understand how to use it. I really didn't think that die could be as good as some folks said, but by golly it really does a great job. If you go with that, go ahead and order a Redding Body Die for the caliber. You eventually will want to set the shoulder back a bit on the cases.

[cw308]

The way I am thinking, right or wrong? From fired to loaded case, there seems to be alot of stretching going on with my RCBS standard dies. With a bushing die .002 less then the outside diameter of a loaded case, when bushing sized with the expander ball used, it could cut down the stretching & any problems with uneven case neck thickness. I'm leaning toward the Redding S type bushing die. Reloads are only for one rifle Remington 700 that was completely trued with a custom M24 5R Rock Creek barrel, only used for benchrest shooting 200 yards. I find reloading a very interesting hobby. I thank you ALL for all the time & info you give me. Chris

[Metal god]

For the most part an expander ball defeats the purpose of the bushing die . You will still get the neck and body in line. The expander ball will change what the bushing sized the neck to so I don't use the expander ball

[243winxb]

alot of stretching going on with my RCBS standard dies.

Very common, over working the brass. Case neck life will be longer with a bushing die. If the necks are not outside turned, using the expander will move the uneven thickness in the neck walls to the outside of the case. You should feel a very light drag from the expander on each case. Test with and without an expander to see what works best. Not all expanders are the same diameter. Spring back of the brass neck is outward after bushing* sizing. Try sizing only 1/2 of the neck.

[cw308]

I will try every possible way, with & without expander ball. Partial , 1/2, 3/4 & full neck sizing. It all starts all over again with a change in something like neck tension. I will keep the load & OAL from the ogive the same. After reading about different neck tension, it started me off again. There is always something new to learn, in the quest for that most accurate load.

[603Country]

I just sized 40 cases with the Lee Collet Die in 260. Very fast. No lubes required. Get one and if you don't like it I'll be surprised. Read the instructions and don't set it to cam over.

If you decide to get that Redding bushing die, don't use the expander ball. And...that die, without bushing, can be used as a body die.

[Bart B.]

There are things mentioned in this thread that ain't quite kosher. Example: bushing die diameters don't make sized case mouths holding bullets smaller in diameter than their difference from loaded rounds' neck diameter. Measure a bushing sized neck diameter before and after seating the bullet. It's bigger after the bullets seated. If you cannot easily push a bullet into a bushing sized case neck/mouth, the mouth diameter is smaller than the bullet.

How much the neck outside springs back from bushing diameter depends on how much the bushing squeezes it down and the elasticity of the brass to spring it back. "Dead" brass springs back very little; "live" brass a lot.

"Interference fit" is the correct term pushing a round thing into a slightly smaller round hole.

"Tension" refers to forces making something lbarger or longer, such as a rubber band. But it's common used to infer the grip case necks put on bullets as the compress around them.

"Compression" refers to forces making something smaller, such as the chamber in an air pump.

Case necks try to make the bullet smaller by compressing its diameter.

All of this can be confusing.

The industry standard for measuring the effects of this is the force ( in pounds) needed on the bullet to start it moving out of the case neck. But only for a short distance because the rifling presents more resistance to the bullets' forward movement than the friction between bullet jacket and case mouth. The force needed to seat bullets is usually different than the bullets release force.

Don't use more than necessary for good functioning and handling.

[cw308]

Bart B , on interence fit. After sizeing my number is .004, after some reading on the subject, .002 is the perfect amount. Am I to tight at .004 for accuracy, or am I making something out of nothing.

[Bart B.]

If the resized case neck outside diameter is .004" smaller than it was before sizing, that may be just fine. The important thing is how much smaller the sized case neck is from a loaded round's neck diameter. If the sized case neck is .004" smaller than a loaded round's neck of the same lot of brass, that's way too much and may scrape off bullet jacket material when bullets are seated; that unbalances bullets. .001" smaller may be about right. I've had some cases when sized their neck diameter's only .0005" smaller than when bullets are seated and they produced excellent accuracy.

If the die's neck (bushing or honed out FL die) is .002" smaller than a loaded round's neck diameter, it'll end up sizing the fired case neck down to about .0010" to .0015" smaller than its diameter because the brass springs back a little from its diameter while inside the die's bushing/neck. A .334" diameter bushing/neck ends up making a fired case neck .3325" to .3330" diameter or there abouts. It'll expand several ten thousandths when the bullet's seated due to the interference fit. As 30 caliber bullets' diameters range from .3075" to almost .3090" depending on make and type, they'll enlarge size case neck diameters accordingly. Loaded round neck diameter equals bullet diameter plus twice the neck wall thickness.

[243winxb]

If the sized case neck is .004" smaller than a loaded round's neck of the same lot of brass, that's way too much and may scrape off bullet jacket material when bullets are seated; that unbalances bullets.

Maybe use on of these?

[Bart B.]

That deburring tool, IMO, does a half-ass job on case "lips" making them sharp and at the wrong angle. They'll scrape off bullet jacket slivers with even a slight interference fit.

After using one to get rid of most of the raw edge left by trimming to length, twist an Easy Out screw remover clockwise in the case mouth. A #5 works good on 30 caliber cases. It adds more radius to that edge. Then pass the case mouth over a spinning bronze bore brush to make that edge round without sharp edges. It'll also clean out a lot of powder residue.

I'll add some pictures later.

Bullets with a tight interference fit go in straight without any jacket being scraped off. They have the same prefect balance as the did in the box they were sold in.

[cw308]

Bart B, my sized case OD is .334, loader case neck OD is .338 . the bullet is a 168 gr. HPBT Sierra 308 cal. Brass is federal FC with wall thickness of .015 So I should be better off with the Redding S type bushing die & bushing .336?