What is causing case to case runout variation??

[270 ftw]

Im getting .001-.006 runout on my sizing operation. Surprisingly equal distribution, in 25 test cases i had 7 cases under .002 thou total runout. 11 between .002 & .004. And 7 between .004 & .006. This is with the expander ball removed just to eliminate it as a variable. These cases have almost zero runout coming out of the chamber. Considering all other variables the same(die setup, lube, brass, etc)... What in the world could i be doing from 1 stroke to the next to have a .005 thou change in runout?

 

[Bc'z]

Bullet not setting up straight be my 1st. guess .
If necks aren cleaned up any anomalies will be pushed to outside of case and show as run out be my 2nd guess.

2 is obvious how to fix.
When you go to seat bullets raise ram while holding bullet with off hand when you feel bullet touch seater stem lower and check to see if its straight before fully seating.
I personally use hornady's seater with sleeve

 

[270 ftw]

Bullet not setting up straight be my 1st. guess .
If necks aren cleaned up any anomalies will be pushed to outside of case and show as run out be my 2nd guess.

2 is obvious how to fix.
When you go to seat bullets raise ram while holding bullet with off hand when you feel bullet touch seater stem lower and check to see if its straight before fully seating.
I personally use hornady's seater with sleeve

This is just on sizing and without an expander. So variations in neck wall thickness which are minimal on the Norma brass im using are pushed to the inside. Fortunately my bullet seating procedure induces no additional run out. At least none that I can measure anyways. Forster benchrest seater kicks butt on that.

 

[mikecr]

Thickness variance, excess sizing of it.

 

[Bc'z]

This is just on sizing and without an expander. So variations in neck wall thickness which are minimal on the Norma brass im using are pushed to the inside. Fortunately my bullet seating procedure induces no additional run out. At least none that I can measure anyways. Forster benchrest seater kicks butt on that.

Bullet is working as a sizing mandrel pushing anomalies outward.
If this ain't happening I'm stumped

 

[270 ftw]

Bullet is working as a sizing mandrel pushing anomalies outward.

Were no where near bullets yet. I'm measuring this run out on the case necks just after sizing.

 

[msinc]

"This is with the expander ball removed just to eliminate it as a variable"

It sounds like you are checking the brass cases and not even seating any bullets yet??? If so then the die has to be bad. With the expander removed and the cases sized that way, then the necks should be showing zero runout and it wont matter about inconsistent neck thickness. At this point the die, if it is right, should be making the cases dead on. If it is then you can usually reinstall the expander, size again and set the expander ball halfway out of the neck and tighten the lock nut. This usually does it, but when you have runout with no expander then the only thing left is the die body itself.
I have taken cases that were sized with the expander way off center, to the point they had almost .010" runout. Remove the expander and run the cases again and you should always get zero. If the size die is right it should always correct runout with no expander installed.
I would contact whoever makes the die and explain what's going on. I had the same problem with a Bonanza die and called Forester. The above is what I was told and it has since proven to be true several times. Good luck.

 

[Uncle Ed]

Is your resizing die full length or a neck sizer, bushing or non-bushing.

 

[270 ftw]

"This is with the expander ball removed just to eliminate it as a variable"

It sounds like you are checking the brass cases and not even seating any bullets yet??? If so then the die has to be bad. With the expander removed and the cases sized that way, then the necks should be showing zero runout and it wont matter about inconsistent neck thickness. At this point the die, if it is right, should be making the cases dead on. If it is then you can usually reinstall the expander, size again and set the expander ball halfway out of the neck and tighten the lock nut. This usually does it, but when you have runout with no expander then the only thing left is the die body itself.
I have taken cases that were sized with the expander way off center, to the point they had almost .010" runout. Remove the expander and run the cases again and you should always get zero. If the size die is right it should always correct runout with no expander installed.
I would contact whoever makes the die and explain what's going on. I had the same problem with a Bonanza die and called Forester. The above is what I was told and it has since proven to be true several times. Good luck.

So im thinking the die has something to do with it as well except that some of them come out with a pretty respectable .001 thou and then the next one will have .006. The die just decides to work properly sometimes and then takes a nap? And believe me I would love to blame the die

 

[Bc'z]

Also check shell holder for debris what's screwy to me is some cases are coming out good.

 

[270 ftw]

Is your resizing die full length or a neck sizer, bushing or non-bushing.

Im using a redding body die to bump my shoulders first. Works amazingly, absolutely no run out after that step. Then running them into a Forster neck size die only. Thats where the trouble starts. And its not the expander which I know is the usual culprit. In fact, just for everyone's information that Forster floating decapping pin with the rubber o-ring set up and interchangeable expander balls seems to be pretty solid setup. I have tested cases after that step many of times and it as well as seating is inducing no additional runout.

 

[270 ftw]

Also check shell holder for debris what's screwy to me is some cases are coming out good.

Im with you on that. I do very vigilantly Q-tip the shell holder because i was thinking something along those lines

 

[Bc'z]

Have you cleaned your die?

 

[Bc'z]

I no I'm stating some obvious things but sometimes they're easily overlooked

 

[270 ftw]

Yup cleaned it every which way. Even mid way through a batch. Always the same step causing this runout. Full disclosure this isn't the only 25 cases I've tested this way. Done it many of times and just cant figure it out. Recently I tried trimming cases before sizing to see if having a more consistent mouth had something to do with that entering the dye more squarely...sadly no results there.

 

[msinc]

Also check shell holder for debris what's screwy to me is some cases are coming out good.

Yeah, I agree, that is a little weird to me too. The dies I've seen bad and do this typically do it pretty consistently. Usually though by the time the case gets that far into the die {up to the neck} it would seem like the shell holder wouldn't affect it too much, but I don't know.
When you think about it, how does the die do it??? I mean, the die is made on a lathe and cut with a reamer similar to a chambering reamer...how could you possibly get that inconcentric??? But, somehow it happens. Maybe when the die is heat treated??? I have seen a few sizer dies that were bad and just would not size a case with out runout on the outside of the case neck.

Edit: I guess my next question would be: how, or what kind of device are you using to check the necks for concentricity????

 

[270 ftw]

Yeah, I agree, that is a little weird to me too. The dies I've seen bad and do this typically do it pretty consistently. Usually though by the time the case gets that far into the die {up to the neck} it would seem like the shell holder wouldn't affect it too much, but I don't know.
When you think about it, how does the die do it??? I mean, the die is made on a lathe and cut with a reamer similar to a chambering reamer...how could you possibly get that inconcentric??? But, somehow it happens. Maybe when the die is heat treated??? I have seen a few sizer dies that were bad and just would not size a case with out runout on the outside of the case neck.

Edit: I guess my next question would be: how, or what kind of device are you using to check the necks for concentricity????

My mind has ponder these things many of hours lol

I'm using the Sinclair micrometer thingy with the sliding rollers that you set the case on and then can measure on the neck or the bullet or whatever you like. I forget exactly what it's called. Not the highest quality tool in the world, but i dont think its the tool. Actually pretty satisfied with it and I think it was under $100 with the dial micrometer

 

[Uncle Ed]

Im using a redding body die to bump my shoulders first. Works amazingly, absolutely no run out after that step. Then running them into a Forster neck size die only. Thats where the trouble starts. And its not the expander which I know is the usual culprit. In fact, just for everyone's information that Forster floating decapping pin with the rubber o-ring set up and interchangeable expander balls seems to be pretty solid setup. I have tested cases after that step many of times and it as well as seating is inducing no additional runout.

A neck sizing die does not support the case body in alignment with the neck. And you sized the case body adding more clearance in the body of the neck sizing die that can increase the neck being off center.

Either switch to a Lee collet neck sizing die and the body die or size once with a Forster full length die.

If you remove the expander from any type full length die and size a case it will be as concentric as it ever will be when measuring neck runout. The neck runout reading increases when you use the expander and push the thickness variations to the outside of the neck. So when measuring case neck runout after sizing with the expander you subtract the thickness variations from the runout reading.

And this is where the Forster full length die excels because the expander can not pull the neck off center. And the Forster benchrest seating die also holds and centers the case body, neck and bullet in alignment for less "bullet" runout.

Or use any full length die with the expander removed and then use a expander die to expand the neck on the upstroke of the ram.

There is no sense in using a body die followed by a standard neck sizing die, because the neck is sized but not held in alignment with the case body.

Weekly Gear Update - 036 Forster Honed Dies

 

[270 ftw]

A neck sizing die does not support the case body in alignment with the neck. And you sized the case body adding more clearance in the body of the neck sizing die that can increase the neck being off center.

Either switch to a Lee collet neck sizing die and the body die or size once with a Forster full length die.

If you remove the expander from any type full length die and size a case it will be as concentric as it ever will be when measuring neck runout. The neck runout reading increases when you use the expander and push the thickness variations to the outside of the neck. So when measuring case neck runout after sizing with the expander you subtract the thickness variations from the runout reading.

And this is where the Forster full length die excels because the expander can not pull the neck off center. And the Forster benchrest seating die also holds and centers the case body, neck and bullet in alignment for less "bullet" runout.

Or use any full length die with the expander removed and then use a expander die to expand the neck on the upstroke of the ram.

There is no sense in using a body die followed by a standard neck sizing die, because the neck is sized but not held in alignment with the case body.

Weekly Gear Update - 036 Forster Honed Dies

Forster FL die is on the way... supposedly. I had one, it was bad. I sent it in, they confirmed this. They had to make a new batch, been over 7 months but last I checked they had sent them out for hardening so I think we're getting close. And hopefully as you say all will be well. In the meantime i ordered the neck die to experiment with neck sizing only but could only get 2 firings before needing to bump the shoulders back. That's how I wound up with a Redding body die lol. I have the lee die... I didn't think about pairing it with the body die, but thats a good idea. I never really liked the Lee die. Feels cheap and I don't like having to put that much pressure on the press plus those ridges it leaves on the outside of the necks bother me. Also i broke one before...but i must admit i have used it to shoot some very tiny groups. Ill give it a try while im waiting.

So I think your on to something with what's causing the run-out. Sounds totally logical. But what about the cases that are coming out acceptable? Are you saying im just getting lucky with some of them?

 

[klamathsteel]

Last year i sent a Forster FL size die back to them that was 20 years or so old. It was not sizing the necks small enough, i could push a bullet in with my fingers after sizing. They checked it out and confirmed it was bad and sent me a brand new one no charge. I have since gone to using a Redding body die to size the body and bump the shoulder followed by a Lee collet neck sizer. I'm really liking the Lee neck die, it is a cheap die and i was sceptical at first but damm it makes some very straight necks with very consistent tension.