Neck Tension

[F. Guffey]

I remember the reloader that started that rumor about the sizing plug pulling the neck forward and increasing head space etc.. etc. And I ask how would a reloader with all of his investigative skill prove the sizing plug pulled the shoulder forward?

We all understand there are time the reloader sizes a case neck that is too small in diameter for the sizing plug, we all understand there are reloaders that pull the sizing plug through the neck when the ram is lowered with 4 squeaks meaning the neck should have been lubed and the neck is passed due for an annealing job.

We have one member that claimed he fired one case 45 times with full loads without serious aftereffects. I ask him if he weighted the case when he started and again when he finished. I think he understood the question but his answer lead me to he made the story up.

F. Guffey

 

[cw308]

Unclenick
I use to use the bushing dies, I gave them a try an went back to the standard die. I will order the Lyman expander ball unit , if you guys use it it must be better. Thanks again.

Chris

 

[Metal god]

Just had a chance to measure the outside diameter of what my .336 bushing die and standard die size the necks down to before expanding The .336 bushing sizes the neck down to ...............................................................................................................................what for it .................................................................................................... .333 and the standard die sizes it down to .326 . This was using once fired Fed GMM brass fired from a Ruger PR .

So that .333 from a .336 bushing seemed odd so I measured the inside diameter off all my bushings from .332 to .337 and all of them are .003 smaller then what is stamped on the bushing . I used to different sets of calipers ( not high end but good ) and I also used my adjustable hole gauge . They all said virtually the same thing . All my bushings are at least .002 smaller they what is stamped on them .

Am I misreading something or doing something wrong ? I really don't have any high end hole gauges . Is there a better way to measure these ?

 

[cw308]

Metal god
I called Brownells just to ask why a .336 bushing would give an outer diameter of .333, they talked about other variables , spring back . I said so in theory the .336 bushing should give a .336 OD. To me a 336 should size OD to 336 doesn't matter if your brass is .015 thick.
Mg are we on the same page or am I missing something?

Chris

 

[Metal god]

Correct all my bushings internal diameter are .003 smaller then what's stamped on the bushing . So it makes sense if Redding anticipates the spring back to be .003 . How ever the cases I neck sized with the .336 bushing came out .333 which is the inside diameter of my .336 bushing so I really don't know what to think . I'll email Redding about it

The thing that upsets me is I never checked these measurements before . I'm not sure it's effected anything other then me having .003 more bullet hold on everything I've loaded using the bushing dies . I generally never play with bushing sizes per loads . I've always measured the outside diameter of a loaded neck then used the bushing marked .002 smaller but used the expander .

I often wondered though why the expand at times had more resistance pulling through then I thought .002 should have . Well it turns out it was really .005 at minimum .FWIW my expander button measures .3065

EDIT Just sent this email to Redding

Hello . I've been using your bushing dies for a few years now and just came across something a little surprising to me . My .336 bushing sizes my 308 neck down to .333 . So I measured the inside diameter of the bushing and it measures .333

This made me measure all my bushings and they are all .003 smaller then what is stamped on the bushing it self . At first I thought I must be measuring wrong but then got to thinking if the .336 bushing sized the neck down to .333 and the internal bushing diameter measures .333 then my measurements must be pretty close .

Can you please help clear up my confusion ? If I want the external diameter of my sized neck to be .336 . Which bushing size should I use ? If different then a .336 bushing , why ?

Thank you

 

[cw308]

Metal god
We are on the same page , my expander ball is .306 , I try to keep things simple using common sense , from your posts your background in reloading is higher the mine. Reloading is my favorite , I have a good understanding but wanting to learn every trick .
In my 25+ years in reloading I've tried different dies , measuring tools . I guess I turned into a reloading nut , l can talk about the shooting sport 24 hrs. a day. Let me know what Reddings response to your email. Nice talking to you.

Chris

 

[Metal god]

Turns out Redding has been closed for the last two weeks or until the 14th and I'll need to resend the email after that . They are not excepting emails at this time .

 

[cw308]

Metal god
I tried calling Redding first , then Sinclair both were closed. Brownells I spoke to a tech . He said there's a lot of variables . Didn't make sense to me , when sizing a fired case OD of .342 with a .336 bushing would size to .333 l could see .337 or even 8 but not 3

 

[Metal god]

Responce from Redding

I received there response yesterday

We get this question from time to time. I can tell you that we hold a very tight tolerance with regards to the bushings and there size. 
The most accurate way to measure the bushings diameter is to use a machinist pin. Using a set of calipers to measure a round surface will often times give inaccurate measurements (bridging effect). 
I have pasted below a link of a discussion taken from our web page regarding bushings. This Q & A discusses the discrepancies that can be found after sizing cases using a particular size bushing. I suspect this is what you are experiencing as purchasing several bushings that are all consistently smaller by .003" would be extremely rare. With that being said if you feel they are out of spec you are more than welcome to return them and we will check them out.

After reading the below link you are left with more questions feel free to give a call or shoot me a follow up email.

Some quotes from the link
http://redding-reloading.com/tech-line-a-tips-faqs/136-bush-size-quest

While it is possible that a Bushing's inside diameter is incorrect, it is very unlikely.  In fact, our bushings are good enough that some folks use our bushings as an "ID standard" to set inside diameter measuring instruments.  We Sunnen hone all of our bushings to a tolerance of -.0005 inch.  (For example, a .333 diameter bushing will measure no larger than .3330 and no smaller than .3325, usually about .3327 to .3328).

 It is very common for reloaders to measure the inside diameter of their bushing with a dial or digital caliper.  Because the inside surface of a bushing is circular, the flat surfaces on the inside jaws of a caliper cannot be used to obtain accurate measurements (known as bridging).  Not to mention the fact that even the best calipers are only accurate to +/- .001.  Using precision ground I.D. Plug Gauges is the only way to accurately measure the I.D. of our Bushings.

Likewise, one cannot measure the neck of a "sized" piece of brass to determine a bushing's size.  Because of springback and the metallurgic properties of brass, the neck of a sized case will not reflect the exact inside diameter of the bushing that it was sized in.  Because of the case differences, both new and as they work harden with age, most serious handloaders end up with several bushings to control bullet tension (bullet pull) closely. 

As always, Redding is happy to examine a bushing that appears defective.  Should we find that the bushing's inside diameter is incorrect, it will be replaced under our Warranty with no questions asked.  Please contact us before mailing any product to us for warranty inspection so that we can be sure that we are solving the difficulty you are having. 

The only issue I have is my necks come out .333 when using a .336 bushing so "spring back can't be happening . Then there's the fact I needed to talk with them once before about there bushings actually sizing the necks smaller then they should . My case necks came out with an hour glass look to them if the expander was not used . I don't remember the exact numbers but believe that center areas of the necks were like .332 while the mouth was .335 . Yet the .335 bushing was used .

Redding actually admitted that this can happen if the neck is sized down more then .005 or .006 at a time( I believe those were the numbers , may have been more in the .007 or .008 range ) . So if your fired outside neck diameter is .344 and you want to size it to .336 you need to size the neck twice splitting the difference , so once with bushing .340 then again with bushing .336 .

I confirmed this to be true and it does work . I'll see if I still have that email exchange . I know I talked about it in a thread but that was a year or two ago and I may not be able to find it .

Either way I'm really starting to be dissatisfied with the Redding bushing die system . It just seems there are more and more little things that can go wrong and they just seem to except it rather then addressing there short comings . Maybe all bushing dies have the same issues , I only have/use Redding .

I'll look for that email exchange or thread I posted in . It may have been in another forum .

Here's the link from here at TFL where I talked about the bushing sizing down the necks more then the size of the bushing
https://thefiringline.com/forums/sh...edding+type+bushing+die+do+this+to+your+necks

 

[Stats Shooter]

Metal God

I take my reloading fairly seriously also, as you may know. It seems to me that this is a lot more effort than it is worth. I am not sure what your objective is, but with a standard RCBS sizing die and carbide expander ball from Lyman, I get very little run-out.

If wanted, you could have some custom dies made sending in fired cases... seems it would be less effort than the bushing system.

 

[Metal god]

It seems to me that this is a lot more effort than it is worth.

At times it does to me as well . How ever I load for multiple 308 rifles and do like the idea of custom tailoring the cases to each firearm and type of load . My hunting loads have a different bullet hold then my match loads and I'll soon be load 308 for semi auto's . The bushing die along with the Redding competition shell holders allow me to pretty much customized the die to each rifle .

As for having to size the neck twice . I don't have to do that often and even when I do It's not actually an extra step . I neck size the cases when I'm de-priming them and I always de-prime and wet tumble before any other case prep is done so sizing the neck down the first time although is an extra step . I incorporate it into a step I'm already doing so it's not a big deal for me to do so .

That all said I'm not apposed to trying other standard dies . I already have a standard Redding FL die . But as stated earlier in this thread . Mine sizes down the neck a lot and then must be expanded . And although I do anneal that still seem to me to be over working the necks more then needed . Maybe RCBS dies will work the necks less .

Which RCBS dies are you guys using ?

 

[cw308]

Metal god
The RCBS die , part number 15501 F/L DIE SET 308 WIN. I also using Redding bushing dies in two steps , first with the neck die .003 then with the full .003 starting from .342 ending with .336 OD bushing. Runout .004
That's why I went back to the RCBS F/S standard die , also using the Redding comp. shell holder set of 5 . I keep my case headspace to .0015 checking with the RCBS Precision Mic. That combo works for me.

 

[Unclenick]

I know common wisdom suggests that calipers are all you ever need to measure anything, it takes real practice to get all measurements right with them. Micrometers with 0.0001" resolution scales really make a lot of these things easier for the average person to do. As Redding suggests, I've never seen an inside diameter measurement off calipers get closer than about 0.002". This is not just because of bridging, but even between to pins in a plate of metal I've found most calipers just don't have the ID jaw's flats ground to the exact same zero as the OD jaws and most folks don't commonly have a convenient way to zero them. Moreover, even on OD measurements many folks, faced with a round object OD to measure that has flex in it, like a case mouth, don't realize how little pressure it takes to distort that object nor how little off-axis the jaws need to be to deflect the caliper jaws themselves. These are reasons 0.001" precision even for OD measurements are commonly given.

Expanding small hole gauges, used with a micrometer by adjusting it down in tenths of a thousandth until light drag is felt pulling the gauge through the measuring surfaces will usually get you within two or three tenths of a thousandth of true diameter. It does take practice to get the feel for it, though.

Pin gauges are an acid test for diameter, but the standard economical foreign-made sets ($50 on Amazon) are in 0.0010" increments and are class ZZ with either +0.0002" or -0.0002" tolerance (you get to choose), so you can't get between-thousandths numbers with them. You can measure tenths by ordering special sets of 25 pin gauges (center value gauge and plus and minus 12 gauges in 0.0001" increments with class X tolerance of 0.00004"). At today's prices (see last page) it is almost $200 n that size range.

The best way for most handloaders to approach the problem is with thimble micrometers. You and measure the resized neck OD before (go all the way around and average the results as most necks are very slightly oval) and again after seating a bullet in it. The difference is very close to the actual interference fit between the neck and bullet, less a tiny bit for stretching thinning out the neck (see table below; it's not much). Once you know what it's going to be with a bullet you only need the resized diameters to judge changes in springback.

Going through all this bother, you can discern why custom rifle builders make special narrow chamber necks. Many cartridge specs allow a range of about 0.004" in neck wall thickness. Chambers are made to accommodate the thickest brass made and still have a little extra room for expansion to release the bullet. Your die maker has to allow it may be at the minimum, so he has the die over-resize. A custom chamber can be made just for average neck wall thickness or for outside turned neck walls and only allow half a thousandth for bullet release expansion. You just have to be able to double check that your necks are right for it and be able to turn down any that are too big. But it cuts way, way down on how much necks expand on firing and way down on how much you need to size them down to hold a bullet again.

I don't know how the use of the term 'neck tension' got started. What is under tension in a neck when a bullet is seated is the circumference of it, which experiences hoop tensile stress and strain. The bullet experiences compression stress from the spring of the neck circumference around it. Combined with the friction between the inside neck and bullet surfaces due to that compression stress, which would be measured in psi, you get a resulting bullet pull. You can control this by the amount of interference fit between the resized neck and the bullet, but you can't control it to an exact psi unless you keep necks annealed to a constant hardness and keep the insides of the neck consistently surfaced so the friction doesn't vary. Not easy tasks for the handloader and probably more trouble than it's worth for most.

 

[Stats Shooter]

Which RCBS dies are you guys using

Honestly, i am just using a standard RCBS sizing die and a lyman carbide sizing ball. I like the carbide ball because you need almost no lube and it glides right up the neck.

I also ensure that there is a little bit of play in the expander ball shaft so that it self aligns coming back up through the neck. I have tried it with the ball tight, and loose, and sometimes when it is tight, I get some runout. I honestly think the runout with a tight ball is partially my fault by going too fast and the shell moves a bit on the shell holder before the ball being pulled through. In which case, runout gets worse. But with a little wiggle on the expander ball, it affords a little margin for error on shell contact with the shell holder and not needing absolutely perfect position.

But, no matter, I just allow the ball to float a bit and don't worry about it. On my dillon presses I am using RCBS dies also, and a lee factory crimp die, and I just remove the decapping pin and decapp on a single stage, then wet tumble, then anneal (if needed) then run through the sizing die with expander ball and no pin. If you keep the pin in, on a progressive press, and it floats, you will break the pin at some point probably.

Plus, I like the idea anyway of knowing I don't have any berdan or those stupid F&S small hole cases (broke a decapping rod on those stupid cases) in the batch binding up the machine.