When sizing cases it is said that you need to size the case inner dimensions at least 0.002” less than caliber as to maintain a proper tension on the bullet. Some experienced reloaders say you must throw out the expander/decapping rod when resizing since it tends to throw out the alignment of the case neck. This is working very fine with my .222 Rem since the sized case is between 0.002” and 0.003” under caliber after sizing. I have tested load on this sizing technique and could not find any difference in pressure or grouping of the .222 Rem.

However, when it comes to my .270 Win it is a totally different story. When I take out the expander/decapping rod, it gives me a measurement of the inner dimensions of up to 0.007 - 0.008” smaller than caliber. I use a Lyman VLD deburring/camphering tool. My question is whether the tension is excessive and what influence it would have on consistency of loads?

Neck Tension after Sizing
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Reloader270
one of us
posted 15 April 2013 20:5015 April 2013 20:50
When sizing cases it is said that you need to size the case inner dimensions at least 0.002” less than caliber as to maintain a proper tension on the bullet. Some experienced reloaders say you must throw out the expander/decapping rod when resizing since it tends to throw out the alignment of the case neck. This is working very fine with my .222 Rem since the sized case is between 0.002” and 0.003” under caliber after sizing. I have tested load on this sizing technique and could not find any difference in pressure or grouping of the .222 Rem.

However, when it comes to my .270 Win it is a totally different story. When I take out the expander/decapping rod, it gives me a measurement of the inner dimensions of up to 0.007 - 0.008” smaller than caliber. I use a Lyman VLD deburring/camphering tool. My question is whether the tension is excessive and what influence it would have on consistency of loads?


I am the fan of bullet hold, I can measure bullet hold, I can not measure neck tension, I can measure the inside diameter of the case, I can measure the diameter of the bullet I can determine interference fit and or crush fit, I can not measure neck tension.

The diameter if the neck after sizing and before necking the case neck up when pulling the neck sizer ball is controlled by the die, you could get a smaller sizer plug. When someone tells you to remove or throw out the sizer plug, respond with ‘Fantastic’ then continue to use the neck sizer plug.

Rational, if you take the advise serious you will began to have trouble chambering loaded rounds, when seating bullets the case is not supported by the seating die, a neck that is not correctly sized will cause the bullet to crush the case and cause a the shoulder to collapse.

I have special seater tools that center the mouth of the case with the bullet perfectly and support the neck, it is almost a can not miss thing, it does not use a body die.

F. Guffey

This may clear up the issue. Its always been refered too as neck tension.
http://riflemansjournal.blogsp...ng-neck-tension.html

quote:

hivelosityone of us posted document.write('<nobr>'+ myTimeZone('Mon, 15 Apr 2013 14:12:22 GMT-0700', '16 April 2013 02:12')+'</nobr>');16 April 2013 02:1216 April 2013 02:12Hide PostThis may clear up the issue. Its always been refered too as neck tension.http://riflemansjournal.blogsp...ng-neck-tension.html Posts: 1413 | Location: OH USA | Registered: 26 June 2000

Sounds good,

hivelosity
one of us
Picture of hivelosity
posted 16 April 2013 02:1216 April 2013 02:12 Hide Post
This may clear up the issue. Its always been refered too as neck tension.
http://riflemansjournal.blogsp...ng-neck-tension.html
Posts: 1413 | Location: OH USA | Registered: 26 June 2000



Back in the big inning Lyman discouraged crimping bottle neck cases, they said nothing about loosening neck tension when crimping goes bad, they described the problem creates less bullet hold, then there were test, the description of the test took a paragraph, there was no mention of neck tension, the test results could not be described as neck tension because they could not measure neck tension, neck tension can be measured as an interference fit or a crush fit. The Aberdeen Proving grounds measured the amount of pressure required to release a bullet, their results were stated in the form pounds as in effort, not in neck tensions.

Again, I can measure bullet hold in pounds per square inch, I can measure bullet hold in dead weight in pounds, even when I know bullet hold in psI I can not find a conversion chart from bullet hold to neck tension.

I know, it sounds cool, ‘NECK TENSION’, I am not cool, I can not measure neck tension. I do not have a standard for measuring tension, Pounds is a standard, the ruler in inches, foots and yards is a standard, the micrometer is a standard, I can measure interference fits, I can measure crush fits.

I thought the Aberdeen test was flawed, there are some that get real excited when posting links to the cold welded bullets etc., etc.. they left out a small detail in the sequence of events between pulling the trigger and the bullet leaving the barrel. They assumed pressure pushed the bullet out and into the throat.

F. Guffey

Neck "tension" isn't bullet grip. A neck smaller than about 1 thou less than bullet diamerter only increases seating effort, the brass itself simply stretches to accomidate anything more. Making a bullet expand its own way into a too-small neck is a major contributor to bullet run-out. I prefer my expander balls to be full bullet diameter because that's what's going back into that hole and it will provide all the grip possible.

Forgive my ignorance but I am confused about this neck tension thing? Does it mean that factory made dies for a certain caliber need to be altered by replacing the expanding ball/decapping rod or.......? Sorry but this is the first time I have heard of all this as I use dies marked specifically for the caliber I load at the time. Can someone please explain this to me? Thanks

LAL. You are good togo, If you want to refine your loads and adjust the tension its a way to change or (adjust) the pressure in a case when the bullet is pushed from the brass. your factory die with the original expander will give about .002 to .003 of grip or (tension).
You can also change this by using a crimp, light to heavy crimps.
A lot depends on the brass as to how much spring it has.
Dave

For all hunting purposes, if you can keep all shots within 3/4 inch at a 100 yard target all is covered.

I have a gage that measures tension, before tension can be measured it has to be converted, by the strain gage as ‘deflection’ the deflection is measured in pounds, some deflection gages measure in 1,000s of pounds, then there is the multiply by 9 +/=.

Again, I am the fan of bullet hold, I want all the bullet hold I can get, there is no such thing as too much bullet hold.

Seater dies: A bevel on the base of the bullet and a bevel on the inside of the case mouth aid in overcoming the interference/crush fit between the bullet outside diameter and the case neck inside diameter, I have made a few seaters that support the neck and shoulder without a die body, alignment between the bullet and case mouth is absolute. I have other seating dies like RCBS competition and gold medal, I have old Herters seating dies that are similar, I have one Lyman universal 7 mm seating die and a Weatherby seating die that is similar. All were designed to overcome the interference/crush fit between the neck diameter and bullet.

F. Guffey

Thanks Gents. After reading the above posts I suffered from tension!! I did at one time experience 3x bullets that were quite loose, I could pull them from the case with my fingers and I applied a LEE Factory Crimp. All the other bullet makes I have used I have had no problems with and mostly neck size my cases. Must admit reloading is a fascinating hobby, I learn something new every day. Thanks to all.

one thing about reloading if it can be tinkered with we will tinker.

quote:

However, when it comes to my .270 Win it is a totally different story. When I take out the expander/decapping rod, it gives me a measurement of the inner dimensions of up to 0.007 - 0.008” smaller than caliber. I use a Lyman VLD deburring/camphering tool. My question is whether the tension is excessive and what influence it would have on consistency of loads?

Probably not a lot of difference except your brass may be overworked and split at the neck prematurely. My 375H&H sizer used to be too small at the neck and I would only get 2-3 reloads before the necks would split. Sent it back to the mfgr and they reworked it to my fired brass.
If your expander is causing runout try loosening the locknut that holds the stem and run a case into the die then tighten the lock nut. This will usually center the expander button close enough for all but benchrest accuracy.

The problem is not the expander ball it is the neck diameter of the sizing die. This is the reason bushing dies were developed.
Changeing the neck diameter on a "fixed" die can be done with the proper equipment, or send the die to Jim Carstensen Dies in Iowa and he will convert your die to a bushing die.

quote:

Originally posted by Reloader270:

However, when it comes to my .270 Win it is a totally different story. When I take out the expander/decapping rod, it gives me a measurement of the inner dimensions of up to 0.007 - 0.008” smaller than caliber. I use a Lyman VLD deburring/camphering tool. My question is whether the tension is excessive and what influence it would have on consistency of loads?

Another possibility is to outside neck turn your brass to have less thickness. IOW if your die without the expander assembly sizes the ID .007" below caliber as you say, and your brass was .014" thick, then you could turn off .002" or .0025" and that would reduce your ID after resizing without the expander

i.e. .014"-.0025"=.0115" per side

then the die will size the ID to .275"

You would get very straight low run out ammo since dies are generally machined with good alignment between case body and necks. The expander creates the problems.

But you do not want brass with a thickness less than .010" per side

Of course you could get a cheap Lee Collet Neck Sizer and have a much better process that neck sizes without lube, low run out and low bullet grip