I have a Redding neck sizer with 4 different bushings for my 7mm rifle. Is there a way of actually measuring the amount of tension these different bushings will exert on the bullets after seating them? I've heard of guys talking of 25 and more pounds of pressure/tension between bullet and case neck. How do they get to this amount?
Ps. all my cases have been neck turned to 0.014" thickness.

If your neck thickness is 0.014", you need to add the bullet diameter (0.284") and 2 times the neck thickness (0.028") together to get the neck diameter of a loaded round - 0.312". I also neck turn and use Redding Competition (neck bushing) dies, and I use a bushing that is 0.002" smaller than a loaded round. I think Redding may now even recommend a bushing that is only 0.001" smaller than the loaded round, but, personally, I like 'em 0.002" smaller.

Thanks TXRam, I'm familiar with the setting up of the dies, all i want to know is how do you physically measure neck tension..is there a special scale for this?

Actual neck tension is impossible to beasure.
Whe you pull a bullet you are measuring a static "break-away". The chamber pressure expands the neck away from the bullet.
Many variables arte involved.
Good Luck!

quote:

Originally posted by THOMAST:
Thanks TXRam, I'm familiar with the setting up of the dies, all i want to know is how do you physically measure neck tension..is there a special scale for this?

The only thing which springs to mind, is that K&M makes an arbor press, which allows a strain gauge to be integrated. It allows you to (at least) COMPARE the force necessary to seat bullets from case to case. That property should be fairly closely related to neck tension.

Most people speak of neck tension the way TXRam does, few actually measure it, and few people therefore quantify any differences they may experience in neck tension. One might think there should be no difference in neck tension with neck turned brass, after all, you have at least reduced any influence from varying neck wall thickness. However, it appears, that over time neck tension may vary. E.g. the seating force necessary may not be the same on cases recently sized as if the cases were sized some time (weeks, days?) ago. There have been references to this effect on 6mmbr.com as well as over on benchrest.com. Besides, brass varies. I always manage to be surprised at the amount of variance one finds in brass from the same lot... I would not be the least surprised, if neck tension also varies from case to case...

FWIW - mike

I am sure there is some reason to know but consider this. If it takes x lbs. to seat a bullet....what ever x may be. Lets say 10 lbs. It is very doubtful that the 50,000 lbs of pressure behind the bullet is going to be adversely effect by a pound or two either way.

quote:

Originally posted by THOMAST:
I have a Redding neck sizer with 4 different bushings for my 7mm rifle. Is there a way of actually measuring the amount of tension these different bushings will exert on the bullets after seating them? I've heard of guys talking of 25 and more pounds of pressure/tension between bullet and case neck. How do they get to this amount?
Ps. all my cases have been neck turned to 0.014" thickness.

The elastic limit of necks is usually ~ .002" change in diameter. The more the neck diameter is changed the more concentricity is lost. The optimum neck bushing is then often ~.002" smaller than the loaded neck.

You could buy .001, .002, and .003" smaller than loaded, and experiment.

I measure neck tension in thousandths of an inch. I use the the bushing .002 smaller than the loaded round diameter, also.

You could always rig up a dead weight tester and measure the holding force. Maybe a peak reading large game fishing scale. Start by drilling a hole through the side of a seated bullet or bullet and case. Perhaps .062" so you can pass through some adequate wire. You can get a lot of braided stainless leader material at hardeware or sporting goods stores. Sounds like a fun thing to me. This is called the direct approachand and is safe to apply with a 6 pack of beer. Don't be too surprised if you find most holding forces over ten pounds. roger

I've reloaded 45 years and never measured neck tension. It was something one just "felt" while seating bullets.

I'm not poo pooing the idea.....maybe there's something to it and it's time to learn new tricks.

If one was to make a 7/8-14 plug for his press and simply make several weights for the handle of his press and use them to determine when the bullet is seated deeper upon such weights added to the handle with a roiund in the holder he would have an idea of uniformity.....maybe not weight but uniformity.
Just an idea.

There really is something to it! For benchrest it is very important but for most rifles, you would never notice anything. However, for revolvers, the difference in the point of impact at 50 yd's between a case with loose neck tension and one that is very tight can as much as 10".
Years ago, I worked up a simple way to sort loads by seating pressure and it worked. I used sorted loads to win Ohio State IHMSA with 79 out of 80 with a .44 SBH.
For that 7mm, I would just get the proper .002" fit and go for it.

Wow! have I opnened up a can of worms?
Kinda like the story of the grandpa who had a very long beard. One day his grandson asked him "grandpa, do you sleep with your whiskers under the covers , or on top of the covers?" The old man never slept again!
But seriously, thanks for everyones' input. The name of the game is uniformity and if you wanted to go to extremes, I guess you could anneal your cases after every shot to standardise neck tension.. and shoot them only at the same time every day under exactly the same conditions. Dont know if I will ever go there..

I don't have an answer to the question, but an interesting thing that happened to me with my 300 WSM when I was loading some 150gr TSX. that I think was caused by neck tension.

I was working up a load and my max powder grouped ok, right at an inch. It started to rain so I didn’t shoot all I had loaded. I went home and thought I would try a different powder next time so I pulled those rounds with a kinetic puller. Well a few weeks went by and I wanted to shoot some, not feeling like working up a new powder I reloaded the same recipe from before with the cases I had pulled the bullets from along with some others to shoot. I shot the pulled cases first and was amazed at the .5 in. groups, holes that almost touched. The rest of what I had loaded for that day shot the 1 in. groups like before.

I have spent some time trying to duplicate that round. I have even tried loading some dummy cases so I could pull the bullet trying to get the same neck tension as I did on that magical day, but I have not had much luck.

Has anybody else had this experience?


Simdow

I use a neck bushing that is the same diameter as the loaded round. When that gets loose, I step down .001". If you use a diameter .002" less than the loaded round, you'll crush the noses of thin-walled bullets like the v-max or ballistic tip.

It is not neck tension alone that holds the bullet in place, but that and the friction between the brass and the copper. That is why cleaning the inside of the case neck is important.

quote:

Originally posted by Ralph Hyrlik:
I use a neck bushing that is the same diameter as the loaded round. When that gets loose, I step down .001". If you use a diameter .002" less than the loaded round, you'll crush the noses of thin-walled bullets like the v-max or ballistic tip.

A bushing of the same diameter??? I would've thought that the brass would "spring back" enough that there wold be little/no tension of the neck on a bullet.

As far as using a bushing 0.002" less than a loaded round damaging a bullet, that has not been the case in my experience. I have used nothing but bushings that are 0.002" less than my neck-turned, loaded rounds, and I've loaded more Ballistic Tips than anything with no problems. I notice that Redding now recommends a bushing 0.001" less than a loaded round, but I could have swore they used to recommend 0.002" less . . .

By her bra size...

quote:

Originally posted by TXRam:

quote:

Originally posted by Ralph Hyrlik:
I use a neck bushing that is the same diameter as the loaded round. When that gets loose, I step down .001". If you use a diameter .002" less than the loaded round, you'll crush the noses of thin-walled bullets like the v-max or ballistic tip.

A bushing of the same diameter??? I would've thought that the brass would "spring back" enough that there wold be little/no tension of the neck on a bullet.

As far as using a bushing 0.002" less than a loaded round damaging a bullet, that has not been the case in my experience. I have used nothing but bushings that are 0.002" less than my neck-turned, loaded rounds, and I've loaded more Ballistic Tips than anything with no problems. I notice that Redding now recommends a bushing 0.001" less than a loaded round, but I could have swore they used to recommend 0.002" less . . .

The very edge of the case mouth will spring back, but the rest of the neck will not. Using the same diameter assures perfect tension for at least three reloads. I load 223 and 22-250, and I don't want any marks on my bullets. If you have a semi-auto, don't use my advice I like mine soft seated.

Redding did recommend .002", but that is too much initially. Maybe after a dozen or so reloads, but not on the first.

quote:

Originally posted by Ralph Hyrlik:
It is not neck tension alone that holds the bullet in place, but that and the friction between the brass and the copper. That is why cleaning the inside of the case neck is important.

Ralph, for interest sake, how do you clean the inside of your neck ?
I brush them with a nylon brush and then wipe them out with a q-tip soaked in acetone.

I have a tub full of mica from Midway which I used as a dry lubricant during sizing at one time, but stopped using it because I found scratchmarks on the necks of the cases after resizing them , probably because I had too much of it on the bottle brush and didn't remove it from the outside of the case neck(I now use Imperial sizing wax)
Do you think this mica could be used on the inside of the necks to after resizing to help keep neck tension variables at a minimum?

THOMAST: Maybe the measuring, in specific, pounds or ounces of neck tension is not the desired end to your question?
Accuracy - is usually what those that dabble in varying neck tension for a particular load/Rifle are seeking.
So, that desired end - accuracy - is measured at the range on a calm day by shooting various loads with varied neck tensions.
Accuracy is a result of uniformity in all aspects of loading and marksmanship.
It would be a simple matter to make up some loads, exactly the same, but having been "tensioned" with a couple different neck bushings.
Best of luck in your search for an answer (accuracy?).
Hold into the wind
VarmintGuy

One thing that helps even out neck tension is to size a little more with the bushings and let the bullet itself expand the brass when seating.
If you do not size enough or with regular dies, expand too much, the brass springback will ruin consistant neck tension.
Annealing brass DOES make it more even but also reduces tension which can make the load act different then it did with hard brass. Then you have to work loads again. It would be a pain to anneal after every shooting.
Unless every case can be sorted for tension, it is a hard battle.
I think even case tension is the most important thing for accuracy of everything else we do. Second would be bullet alignment (no wobble.) Or maybe the importance is equal!
A big problem is that as brass work hardens and we load some cases more then others, they get different. I have never been able to keep brass separate for how many times it was shot.
Even new virgin brass is never really the same case to case.
In way over 50 years of shooting muzzle loaders, I never had the problems caused by the brass case. It is a fact of life that we will never overcome.

I forgot to say that it does not matter if neck tension is a little less or a little tight. As long as it is even in all of your loads, it will be accurate. Mix them and groups spread.

I cross my thumbs at the adams apple and interlace my fingers at the cervical spine and then watch the protrusion of the eyeballs. It works well for me

Thats how my friend shoots. He makes grooves in the ground big enough to plant taters.

Thomast.
The March 06 issue of PS Shooting features an article about neck tension. A scale was set up and cases prepped to take a piston and a plunger inserted through the primer pocket.

The cartridge was raised against the plunger with a small press. the plunger pushing against a digital scale recording the force in lbs to push out the bullet.

Forces up to 60 lbs were recorded. The test included several neck treatmnets to get uniform neck tensions. As you might suspect neck tension greatly effects accuracy. The article deals with the 6ppc BR cartridge.

Graphiting the inside of the necks established low SD in static friction in case necks. Interesting write up.

Myself using only moly plated bullets 1 thou greater neck tension greatly improves ignition and accuray. I use a 3thou smaller bushing for my 6ppc 30BR and the 6x47 and the 25 Hunter.

quote:

Originally posted by VarmintGuy:
It would be a simple matter to make up some loads, exactly the same, but having been "tensioned" with a couple different neck bushings.

VarmintGuy - what you say makes the most sense in the absence of a numerical value of neck tension. It seems that some sort of coating in the bullet/neck interface does help in reducing the SD.(graphite and moly were mentioned, I'm not keen to start with moly) What do you think of mica? Or is it too abrasive?

I use graphite, the idea was to make the expander button slide out nicely.
The Lee collet n/s uses were bragging about not having to use lube.
Maybe they will get even more accuracy if they start lubing. Wouldn't that be a shame.

quote:

Originally posted by JAL:
I use graphite, the idea was to make the expander button slide out nicely.
The Lee collet n/s uses were bragging about not having to use lube.
Maybe they will get even more accuracy if they start lubing. Wouldn't that be a shame.

Hey JAL

I always thought that with the force necessary to seat a bullet that the bullet would remove any kind of dry lubricant and scrape it back into the case. I could see how the graphite in the neck would make bullet seating easier by being pushed on the leading edge of the bullet base as it is being seated. But then it ends up in the powder. Maybe some of it is left in between the bullet and the neck, especially with boat tail bullets.

The lube I don't want in the neck is the oily case lube kind. Do you use graphite to lube for the expander ball or for bullet seating?

The way I do it is to have a dry neck and steel wool it completely and thoroughly removing all debris, residues, burrs and scratches. Seems like it would be more consistant to know that there is nothing but bare brass rather than chance uneven distribution of dry lubricants.

BTW, my accuracy was improved after I started using Lee Collets. Maybe it was less runout or maybe it was a completely clean inside neck.

quote:

Originally posted by THOMAST:

quote:

Originally posted by Ralph Hyrlik:
It is not neck tension alone that holds the bullet in place, but that and the friction between the brass and the copper. That is why cleaning the inside of the case neck is important.

Ralph, for interest sake, how do you clean the inside of your neck ?
I brush them with a nylon brush and then wipe them out with a q-tip soaked in acetone.

I have a tub full of mica from Midway which I used as a dry lubricant during sizing at one time, but stopped using it because I found scratchmarks on the necks of the cases after resizing them , probably because I had too much of it on the bottle brush and didn't remove it from the outside of the case neck(I now use Imperial sizing wax)
Do you think this mica could be used on the inside of the necks to after resizing to help keep neck tension variables at a minimum?

I clean the case necks with a bronze brush. This scrapes out the carbon and allows metal-on-metal contact. Metal-on-metal offers the greatest amount of friction for consistent ignition. If you start to lube the necks, then you better seat into the lands, otherwise your ignition will become erratic.

This boils down to your reloading preference. Most factory throats are long, and attempting to load ammo into the lands is silly because very little of the bullet's shank remains in the case neck. Custom chambers with short throats offer more options. You can lube the necks, and seat into the lands for better consistency. Bullets jammed into the rifling offer plenty of resistance, and a lubed neck removes the brass tension/friction variables.