Concentricity Issue

[hogan]

If your sizing die is delivering cockeyed brass after sizing, when brass have -0- runout before they are sized; and this happens no matter if you use a sizing button or not, then you have a press/die mount issue.

Other variable is very distressing; maybe die was done off-center?


One reliable way of assuring alignment of sizing button is to tighten the decap rod when the decap pin is through the flash hole.

Not familiar with the Forster press, but believe they use a system which does not cause the die to bear against the press frame... Maybe the press and die system is out of alignment? Does this problem occur with other brass? Are you checking other brass for concentricity issues?

 

[Jayhawker]

The fired brass has zero runout going in and if I don't use the expander, zero runout when it comes out. The problem is obviously the expander or the way I've got them set-up. After sizing, I can realize acceptable runout by using an expander separate from the die.

 

[bigedp51]

Jayhawker

I replaced many of my RCBS expander and spindle units with Forster expander spindle units and I'm getting .001 or less neck runout. Try adjusting the expander up or down until you get reduced runout readings and not have to size the cases in two operations using a neck expander die.

 

[Jayhawker]

bigedp51:

Your expander from the Forster die sits much higher than mine, probably as much as a 1/2". I'll have to give that a try. Forster, in their instructions with the FL die, is very specific about where the expander should be and I've used that as a guide thus far. As soon as I get some more fired cases, I'll see how it goes. The weather here lately-30mph wind-has not been shooting conducive.

Pete

 

[bigedp51]

Jayhawker

The principle behind the high mounted expander is the neck of the case is still inside the neck of the die and held firmly in position when the floating expander enters the case neck. This centers the expander and prevents the expander from pulling the case necks off center.

If you have your runout gauge out and check for runout after each expander adjustment you will be able to get to *zero runout.

*Depending on how much coffee you drink and how shaky your runout checking finger is.

Forster Full Length Sizing Die Cutaway (look at where the expander button is, in relation to the base of the dies neck area)
https://www.youtube.com/watch?v=RgIfzsH8N6k

 

[BoydAllen]

If you have a RCBS one piece FL die, and want to play with the raised expander, which is the best position for a decapping stem mounted expander, you can polish the expander to a mirror finish, keeping in mind that the work of expanding is done from the top of the expander down to its largest diameter, decap a few cases separately, and raise the RCBS decapping stem so as to position the expander in the high position. The way to do this is to start with the stem and expander in their normal positions, lube a case and run it fully into the die. At that point, with the case still in the die, raise the stem/expander to the point where you feel the expander stop on the bottom side of the neck shoulder junction , and then lower it perhaps a 1/16 of an inch or a little more. This should allow you to experience the advantages of a high expander without having to wait or spend any money. Of course, if you like it you can buy the Forster replacement that will eliminate having to decap as a separate step. Another thing that Forster does on their dies is to put an O ring under the lock nut on the decapping stem, to allow the expander to center itself as it enters the neck. All that you need to have this feature is an O ring that is the correct size to fit the expander stem. While you are at it, you can put one under the die lock ring, slightly compressed, or use a Lee lock ring. Sometimes we have to work with what we have, and try different things to make it work better.

Correction: Forster uses a rubber washer to secure the adjustment with out having to resort to tools to secure or loosen it. What I said about the O ring still applies.

 

[bigedp51]

BoydAllen

Below on the left is the RCBS expander in its highest position and on the right is a Forster expander unit. You can't raise the RCBS expander high enough to duplicate the Forster expander unit because the stem is not designed the same and threaded as high as the Forster unit.

Meaning the neck of the case will not be supported and centered by the neck of the die when expanded because the expander is far too low. This is why I bought the Forster expander on the right for the RCBS die that doesn't allow the expander to pull the necks off center.

I also used a Lee lock ring on the RCBS die to allow it to float and still lock in position when made finger tight.

If anyone wants to duplicate a Forster die then you need a Forster expander and spindle unit to reduce neck runout.

 

[CatShooter]

"Another thing that Forster does on their dies is to put an O ring under the lock nut on the decapping stem, to allow the expander to center itself as it enters the neck. All that you need to have this feature is an O ring that is the correct size to fit the expander stem. While you are at it, you can put one under the die lock ring, slightly compressed, or use a Lee lock ring. Sometimes we have to work with what we have, and try different things to make it work better.

Correction: Forster uses a rubber washer to secure the adjustment with out having to resort to tools to secure or loosen it. What I said about the O ring still applies."

Boyd... Forster doesn't use rubber rings anywhere (unless they just started in the last few weeks).

I have a lot of red die boxes, cuz Forster is one of my favorite die peoples - and none of them have rubber anything on them... and their parts list does not list anything rubber either.

Maybe you are thinking of Lee (Gag).

 

[bigedp51]

CatShooter

Drink another cup of coffee, the Co-Ax Washer (W-10) below is rubber and allows the spindle to float.
Please do not get as senile and have as much memory loss as fguffey..........no one else will think my jokes are funny. :'(
(THE RUBBER WASHER SHOULD FIT THE DIE LIKE A RAT TURD IN A VIOLIN CASE)

 

[BoydAllen]

Ed,
This may be a caliber by caliber thing. Before I wrote the post, I got out a RCBS .222 FL die and was able to raise the expander to the point where it came into contact with the neck shoulder junction.

This morning I did some measuring and figuring to make sure that I had not simply come to the end of the decapping stem threads instead of running into the inside of the neck shoulder junction.

Reaching down into the top of the die using the bottom of my dial caliper like a depth mic, the top of the neck portion of the die starts at a depth of .818". The body of the die is 2.414 long. Adding the depth to where the case sits on the shell holder (which is in contact with the die when bump is properly adjusted for this particular rifle) .125 we have the case extending into the die the trim length minus .125 which is 1.690 - .125 = 1.565 With the expander adjusted up as high as it will go, the top of its working diameter is about 1.070 down from the top of the die. By rough caliper measurement, the body of the case, up to the base of the neck is 1.400 inches long, and extends about 1.275 into the die. If we take that figure, and subtract it from the length of the die body, we have the outside of the base of the neck about 1.139 down from the top of the die. If we subtract approximately .020 for the thickness at the bottom of the neck shoulder junction ( a guess) from the extension from the bottom of the die, the inside of the shoulder ends up about 1.159 from the top of the die as compared with the top of the working part of the expander at 1.070 down from the top in its highest position, which means that I can insert a case fully into this die, and raise the expander up to where it is stopped by the case with room to spare.

 

[CatShooter]

CatShooter

Drink another cup of coffee, the Co-Ax Washer (W-10) below is rubber and allows the spindle to float.
Please do not get as senile and have as much memory loss as fguffey..........no one else will think my jokes are funny. :'(
(THE RUBBER WASHER SHOULD FIT THE DIE LIKE A RAT TURD IN A VIOLIN CASE)

OK... (no coffee... I gave it up two weeks ago, after 40 years of 3 pots a day )

I have Forsters without and my last set (which is still NIB) does - but it does not serve to let the stem wobble - it keeps the top lock nut from coming loose - the stem (on mine) does not move or self-align.

 

[BoydAllen]

FYI Lee and Hornady dies are designed so that you can try the high expander position as long as you are willing to decap as a separate step. I think that the Hornady expanders are the best out there.

 

[bigedp51]

This all started when I wanted less neck runout on my 30-06 cases loaded for my M1 Garand. I experimented raising the expander button on my RCBS dies and adding rubber o-rings but was not satisfied with the results.

I ordered a Forster 30-06 full length die with the high mounted expander and was amazed at the results and much lower neck runout. I did want to buy all new Forster dies to replace my existing dies so I ordered the Forster expander and spindle units for much,much less and again reduced the neck runout on the modified dies.

Bottom line I had already played around with the existing expanders and spindle assemblies on my RCBS dies and ordered the Forster units and got much better results. Meaning on the RCBS dies I tested the stock spindles were not made to raise the expander far enough to duplicate the Forster design, and not worth playing with to reduce neck runout.

 

[paulh]

If you have a RCBS one piece FL die, and want to play with the raised expander, which is the best position for a decapping stem mounted expander, you can polish the expander to a mirror finish, keeping in mind that the work of expanding is done from the top of the expander down to its largest diameter, decap a few cases separately, and raise the RCBS decapping stem so as to position the expander in the high position. The way to do this is to start with the stem and expander in their normal positions, lube a case and run it fully into the die. At that point, with the case still in the die, raise the stem/expander to the point where you feel the expander stop on the bottom side of the neck shoulder junction , and then lower it perhaps a 1/16 of an inch or a little more.

This is exactly what I had to do with my RCBS 30-40 FL sizer. The 30-40 case has such a long neck, that setting the button in the conventional position was unsat. Neck runout was horrible and you could see the neck wobble on the RCBS concentricity gauge. Didn't matter the brand, I have RCBS, Hornady, Redding FL and Neck sizers, all shifted the neck wonky on the Krag with the button in the standard position, no matter what I did. With the technique B. Allen is describing, I could keep the runout averaging .003 and under. This was with a Lee Turret press, RCBS sizer and seater.


This last weekend I put my new Forester coax in operation. The first rounds I ever put together on the coax were three dummy 30-40 rounds. With the coax, the adjusted RCBS sizer, a new Forester Ultra Seater for the Krag, case/bullet runout averages .0015-.002.

However, I resize the 8x57 differently. The neck on the 8x57 is considerably shorter than the Krag case, which is why the following method works so well with it. I use an RCBS sizer w/ the expander and rod taken out, a Redding FL w/ tapered expander, and a Forester Seater. Once the case is FL sized in the RCBS w/o expander rod, it goes into the Redding die w/ tapered expander just enough to pop open the case neck. Cases were coming out with an average of .001-.002 runout. I tried the adjusted expander method with the 8x57 RCBS FL sizer as explained and the average was .003-.004.

Here's a couple vids to laugh at that explains my ghetto method better. However the Coax press is night/day over the Lee press.

https://www.youtube.com/watch?v=vGEXfwopfhY

https://www.youtube.com/watch?v=IXFoEjbI4GA