My fired Lapua 6 BR brass is going into the Redding sizing die with .000" concentricity but coming out anywhere from .002"-.005" out of round. Ball mic shows the neck wall thickness to be even all the way around. Any ideas? I was wondering if when the die pushes the shoulder back .002", is it doing so unevenly "tilting" the neck.
Concentricity Issue
- Thread starter Jayhawker
- Start date
If you are using the expander ball you could try resizing without the expander ball and see what you get. If the expander ball is the problem then you could go to an expander mandrel. Also run out may not be an issue depending on the type of shooting you are doing. There is a lot of talk about run out but not much data on what it is worth on the target. Given a choice between straight ammo and crooked ammo I will take straight ammo every time. But for some applications it may not matter.
What kind of press and shellholder are you using? Are you locking the die down or letting it float with an o-ring under it.
bigedp51
A bushing die can cause runout if it sizes the case neck .005 or more in a single sizing step.
If you do not have a tight neck chamber you would be better off using a Forster full length die with the high mounted expander.
If you do not have a tight neck chamber you would be better off using a Forster full length die with the high mounted expander.
The press ram/shell holder may not be at all well centered under the die due to fact that plenty enough looseness exists in fit between the die and the press threads that the die body can easily end up locked down cocked out of alignment and off center with the press ram.
Loosen the die lock ring and apply upwards pressure to the base of the die so it’ll will top out in and tend to center and square itself in the looseness that exists in all 7/8 -14 threads. Use a known flat as it can be flat washer in between the shell holder and the base of the die to make up the difference if for a proper shoulder bump the die needs to be backed up so far that the shell holder is not going to reach the base of the die with the press ram fully extended. I give it a gentle bounce or two to aid with centering the die and then hold the ram pressure against the die while putting the just snug on the die lock ring.
Be rid of all die lock rings using a setscrew threaded up against the die’s threads, buy new split ring lock rings that clamp about the die evenly without trying to shove the die off center. Replace the shell holder retaining clip with an o-ring that’ll retain the shell holder but also allow it enough freedom to better align with the die.
The same logic and methodology works to square and center the de-cap/expander rod in the die’s threads before locking it down. Stop the ram on the down stroke with the expander pulled ~ half way through and leaving it still trapped within the sized and previously checked for good concentricity neck. Using the ram via the still trapped expander ball, apply an upwards pressure to the de-cap/expander stem to top it out in the built-in slop that exists in those threads. Hold what you got (topped out) and just snug that lock ring.
Loosen the die lock ring and apply upwards pressure to the base of the die so it’ll will top out in and tend to center and square itself in the looseness that exists in all 7/8 -14 threads. Use a known flat as it can be flat washer in between the shell holder and the base of the die to make up the difference if for a proper shoulder bump the die needs to be backed up so far that the shell holder is not going to reach the base of the die with the press ram fully extended. I give it a gentle bounce or two to aid with centering the die and then hold the ram pressure against the die while putting the just snug on the die lock ring.
Be rid of all die lock rings using a setscrew threaded up against the die’s threads, buy new split ring lock rings that clamp about the die evenly without trying to shove the die off center. Replace the shell holder retaining clip with an o-ring that’ll retain the shell holder but also allow it enough freedom to better align with the die.
The same logic and methodology works to square and center the de-cap/expander rod in the die’s threads before locking it down. Stop the ram on the down stroke with the expander pulled ~ half way through and leaving it still trapped within the sized and previously checked for good concentricity neck. Using the ram via the still trapped expander ball, apply an upwards pressure to the de-cap/expander stem to top it out in the built-in slop that exists in those threads. Hold what you got (topped out) and just snug that lock ring.
OleFreak said:
Interested to know how a lock ring can cause a die body to be "off center" when the lock ring is NOT attached to the press… so can't apply a sideways force (to the die).
BoydAllen
Gold $$ Contributor
First things first...is your FL die a bushing model or one piece? If it is one piece. try decapping first, sizing without the expander and mandrel, and then lubing your necks and expanding them with a expanding die and mandrel that you would use to prepare for neck turning. I have tested this and it helps quite a bit.
On the thing about lock rings, multiple tests have shown some slight improvement in concentricity by placing an O ring under a conventional lock ring. That is the reason that Lee lock rings have O rings.
If your die is one that works with bushings, what is the fired diameter of your necks, and what is your bushing size. When the amount of reduction becomes too large, as it may be with a factory chamber, it can cause concentricity issues, and there may be better ways to size.
On the thing about lock rings, multiple tests have shown some slight improvement in concentricity by placing an O ring under a conventional lock ring. That is the reason that Lee lock rings have O rings.
If your die is one that works with bushings, what is the fired diameter of your necks, and what is your bushing size. When the amount of reduction becomes too large, as it may be with a factory chamber, it can cause concentricity issues, and there may be better ways to size.
This is a one piece, FL die and the press is a Forster so I'm not sure the o-ring suggestion would work as far as putting it under the die. The way they've got it set-up, it appears to float anyhow. Nonetheless, I think I may have properly sized mandrel and expander and will give that a try. Thank you. FWIW, the other calibers I use this press for-.308 and 6X47-work perfectly.
BoydAllen
Gold $$ Contributor
Given the press that you have, my O ring comment would not apply. Also, I am not all that confident about the expander die suggestion. It has been my experience that for expanding with a die and mandrel letting the die float as much as your press does is counter productive, but that was for a necking up operation making 6PPC brass. For a same caliber expansion there may not be a problem. The only way to see would be to try it. Are you lubing the inside of your case necks? You might also measure a neck sized without the expander and one with. I would be interested in the numbers. The other thing that I would like to know is how straight the case sized without the expander would be.
bigedp51
Jayhawker said:
I take it you have the full length Forster die with the high mounted expander. I ordered several Forster high mounted expander and spindle assemblies for my RCBS dies and it took a few up and down adjustments until I was getting less than .001 runout measured at the case neck.
So if this is a new Forster die and you took it apart for initial cleaning the expander may have moved and is no longer being centered by the neck of the die.
deadwooddick said:
There’s fair amount of mechanical advantage going on with a thread pitch like that of the little pipsqueak setscrew. Cranked on hard enough and that setscrew will have little trouble shoving the die off to the side of the lateral slop within the threads joining the die and lock ring. More likely it’ll ‘bite’ when screwing die back into the press, expecting the previously set lock ring to park the die back in the exact same position as before.
I got hold of a Forster FL die to test along side of my Redding FL die. I set-up the dies to make sure they were adjusted correctly. Measured the shoulders before and after as well as in the actual firearm chamber. The results: Nothing changed with the Redding die. Shells went in at 0" concentricity and came out anywhere from 3-.005" out of round. Did the same with the new Forster die and was still getting 2-.003". However, when I ran the shell through the Forster die twice rotating the shell 180 degrees, it reduced the out of round to 0-.001". I tried the same thing with the Redding die but got no notable results. I'm not crazy about having to size every shell twice but I guess I'll do what I have to do. May try expanding expander/mandrel route.
bigedp51
Jayhawker
Sorry for these question but are you lubing the inside of your necks.
And what is the diameter of the Redding and Forster expanders.
Sorry for these question but are you lubing the inside of your necks.
And what is the diameter of the Redding and Forster expanders.
I have found that most of the runout i get is in the body of the case behind the shoulder. Run your case neck on the concentricty gauge and you will find little runout on the neck, then keeping the neck on the your gauge check the runout on the case body. I find that my runout on bullet is usually under .0015 but the case body has a lot more. A full length sized case is centered in the chamber by the bullet in the throat so if your runout is in the case body it is nothing to worry about.
CatShooter
Jayhawker said:
When you say "out of round" do you mean oval (two gauge dips on one rotation), or do you mean round (one sine dip on one rotation), but off of the rotation axis??
I set the dial indicator so the needle starts on a given spot and then slowly rotate the shell. It may stay on the point briefly but then gradually moves the needle to a maximum deflection and then back to the starting point. That's about the best I can explain it. I use the center of the neck as a measuring point.
Upgrades & Donations
This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.