Neck Tension vs Accuracy

[jlow]

Jim – if your neck gives you .2615, even if your pressure ring pushes out and there is no spring back, you should still have .2610” external diameter and .2406” internal diameter, so if your shank is 0.2432, you should still have .0026” grip.

If you are not seeing any grip after the pressure ring goes through, re-measure everything, the neck external diameter, the neck thickness, and the bullet diameter. One of those numbers will tell you what is happening.

Larry, not trying to tease but when I run across a problem like this at work, it usually brings a smile to my face. The reason is unlike some problem that are murky in terms of a cause, the problem you have is easily solvable.

You have every piece of evidence (bushing, case neck, and bullet) in your hands. If you have the right measuring tools and the know how to use them, there is absolutely nothing stopping you from figuring out why you have your problem.

 

[Joe Salt]

snakepit the reason I lube the inside of my necks, is to get consistent seating depth. I believe with a dry neck you are galling the bullet. kind of like putting your bolt in gun with no grease on the lugs. Matt just like we were talking at the range, I think sometimes with a fresh chamber job, there sometimes on the ruff side and tend to hold the bullet. Thats why I JB. the throat as soon as I get a new one. Jim there are a lot of top shooters that go even tighter than you, then run an expander through the neck to the size they want. And I believe that is on the decapping rod when they pull it back up. There are all kinds of ways to solve problems, some work some don't.

Joe Salt

 

[johara1]

Guys, I have had this issue for two years and 12 barrels and the same result and i fooled a little this morning and i thought i had it …. one case held and 4 pulled. So after the national i will try it again and i will FF new cases again, maybe. Don't get me wrong this shoots great jumping but i just don't like leaving anything on the table…….. jim

 

[daniel brothers]

does it only happen with this one bullet... ?

Have you tried other brand bullets...?

 

[jlow]

Guys, I have had this issue for two years and 12 barrels and the same result and i fooled a little this morning and i thought i had it …. one case held and 4 pulled. So after the national i will try it again and i will FF new cases again, maybe. Don't get me wrong this shoots great jumping but i just don't like leaving anything on the table…….. jim

I don't understand why are you not measuring their diameters to figure out where your problem is?

 

[johara1]

jlow, I measure every way possible and it should work but it doesn't, a loaded round is .2645 ahead of the pressure ring no matter what bushing you use……. jim

 

[johara1]

does it only happen with this one bullet... ?

Have you tried other brand bullets...?

Just the Spencer,,,,,,,,,, jim

 

[BoydAllen]

I have seen bullets that effectively did not have any parallel sided shank. They tapered slightly from the the front of the pressure ring, and then at a greater rate in the area that would be designated as the ogive. I guess what I am asking is how this bullet profiles in front of the pressure ring. Also, am I incorrect in thinking that for there to be a complete circle where the bullet contacts the throat, that the groove diameter of the barrel has to be smaller than the bullet at the point that it is marked?

 

[jlow]

jlow, I measure every way possible and it should work but it doesn't, a loaded round is .2645 ahead of the pressure ring no matter what bushing you use……. jim

Jim – a bit hard to understand how you can measure all the components and cannot figure why you have a problem. If your bullet is sliding freely in your neck then it has to be one or more of the following:

1) The neck has not been sized down enough.
2) The neck has been opened up after sizing for some reason.
3) The neck thickness has changed.
4) The bullet is undersized.

Other than these four possibilities, I cannot see any other reason why your bullet is not being held so finding which one is root of your problem is the first step to trouble shoot your problem.

 

[johara1]

jlow, when the bullet moves a little…. i'll say a 1/16 just a number maybe less, the bullet is free and you can push it back in till it clicks into where it was originally seated. the neck has been sized as far down as .2595, neck never opened up ever. Neck thickness has never changed and retuned to make sure they don't flow. Bullets are the same 6000 of them. I don't care how much you size the neck down you do not gain more spring back………….. jim

 

[BoydAllen]

Does the sized part of the neck extend well past the pressure ring? If the pressure ring passes through the sized part of the neck, and beyond, there will be a problem getting enough neck tension, and the constant shank taper would exacerbate it.

 

[johara1]

Does the sized part of the neck extend well past the pressure ring? If the pressure ring passes through the sized part of the neck, and beyond, there will be a problem getting enough neck tension, and the constant shank taper would exacerbate it.

Boyd, I'm aware of that, If it did you can push the bullets in with your fingers. As i stated before i ran test like that with different bushings from .001 nt. to .004 nt. once seat them past the sized part you can push them all in with your fingers. If the spring back isn't sufficient to contact the bullet after the pressure ring goes through all the extra grip holds nothing. They all mic the same ahead of the pressure ring .2645,no matter what bushing is used……… jim

 

[BoydAllen]

I guess my point was that I don't think that it is correct, or particularly functional to either have a throat length or die setting that has your pressure ring beyond the sized section. Essentially that loading that way is a fundamental mistake and to be avoided unless the small amount of neck tension that it leaves you with produces accuracy that you cannot get any other way. I would deal with that first by lowering the bushing in the die, or if that would not do it, cutting the freebore longer.

 

[johara1]

I guess my point was that I don't think that it is correct, or particularly functional to either have a throat length or die setting that has your pressure ring beyond the sized section. Essentially that loading that way is a fundamental mistake and to be avoided unless the small amount of neck tension that it leaves you with produces accuracy that you cannot get any other way. I would deal with that first by lowering the bushing in the die, or if that would not do it, cutting the freebore longer.

Boyd, Maybe i'm not painting a good picture, I did that as a test, and i found as stated above no matter what neck bush you use the out come is the same not enough spring back. You get a better read that way …… they were not ever fired that way. The bushing is down as far as it can go and i have .135 free bore. When i shoot them jumped they are .020 back in the neck and they don't reach the unsized area…….jim

 

[Joe Salt]

Boyd I think I know what you are saying, Jim I use a white graphite powder when I set up my bushing die.I Put some around the neck, run it up in the die then you can see how much of the neck is sized. Mine will do the whole neck, so if you can only size 3/4 of the neck and you are seating the pressure ring past that, yes you have a problem!

Joe Salt

 

[BoydAllen]

On the other hand, with pressure rings in sized portions of necks of my PPC, there are differences in seating force, force to pull (this shows up when seating near jam.) and tune. My necks are about .0081.
It would seem that for that specific bullet, if more than minimal bullet pull is needed, that having the pressure ring in the sized part of the neck is a requirement, and that if very light pull gives excellent accuracy, having it out of that area may be an advantage in that it makes neck thickness, hardness, and bushing size much less important.

 

[Alex Wheeler]

Jim, all you need to do is increase neck to bullet friction. You know you can't get the spring back so just stop brushing the inside of the neck. That will double the seating force/bullet to neck friction.

 

[johara1]

Jim, all you need to do is increase neck to bullet friction. You know you can't get the spring back so just stop brushing the inside of the neck. That will double the seating force/bullet to neck friction.

Alex, What nobody can grasp is i can have 50lb. of seating force and it still only hold the bullet at the pressure ring. That is why i did the test seating the pressure ring past the sized part forward of that has NO grip no even a .259 bushing. No matter what tension you put on it it doesn't hold past the pressure ring once it goes through. No matter what you do or add or size to it will not make a difference on the area that does hold the bullet. The area that holds the bullet when seated is very small ....just the pressure ring. I'm aware that light neck tension is accurate and that is where i'm at (jumping) them,20 lb. seem to be the best with low ES. and small groups. I do know if i could figure it out and after 4 reamers and a bunch of barrels it set records jumping but i do know it will shoot better in rather than jumped but it is not reliable ………. jim

 

[johara1]

Larry, Yes i tried 4350 a long time ago and it will not shoot with RL-15 …… nothing will in the Dasher. I can go faster but it will not shoot as good, Seems to shoot in the wind better right were i'm at with the Spencers……… jim

 

[Alex Wheeler]

Jim I know the only thing holding the bullet is the pressure ring, same thing in my gun, shot all season that way. I also have a 284 and with 180 vlds I have the same problem, after the ring goes past the sized part of the neck the bullet just falls in. Your issue is the bullet moving when your try to jam ,010 right? Does it matter what holds the bullet if it holds? Thats why I suggested to not brush the neck, the extra friction may help from unseating the bullet.