Runout after using k&m expander mandrel

[josebd]

I use it on .223 lake city brass,get very if any runout.
With .308 lapua brass .004 runout?
I'm not turning necks,I just use them for consistent neck tension

 

[Dusty Stevens]

Mark one spot on the brass in the press then the high side after expanding. Then turn the case 180deg in the press and see if the high side is 180deg out

 

[josebd]

Ok I’ll try that

 

[josebd]

I’m resizing with fl die without expander ball,then run through expander mandrel

 

[jonbearman]

If you are tightening that expander die in the press try it just screwed in with just light finger pressure on the lock nut so it kinda floats.

 

[Uncle Ed]

Check the neck runout after sizing and again after expanding the necks. This will tell you where the runout is coming from.

 

[SEM]

I have been using Lyman M dies and getting similar run out I think it is my shell holder that is part of the problem not fully supporting the case slightly tipping toward the opening and or not centering with the die, most notable on 223 cases, I leave the set nut loose too, it does help.
I was also thinking of tapering the lead more, for now just using the regular expander

 

[T-shooter]

Check the runout before and after expanding. Mark the high side. You may also try running the bras on the expander twice, once, then rotate 180° and then again. Ans as was suggested, leave the expander a little loose in the press so it can float. I get no additional runout using mine and I use it as the final sizing tool to set the tension.

 

[T-shooter]

I forgot to ask, do you have the center screw set so the brass cannot bottom out on the neck? That could cause runout.

 

[josebd]

I forgot to ask, do you have the center screw set so the brass cannot bottom out on the neck? That could cause runout.

Yes I do

 

[josebd]

The die for the expander mandrel just screws in the press ,it’s loose ,no lock ring

 

[josebd]

I can’t remember last year what I did,maybe I ran them through the fl die with the expander ball,then ran through mandrel?

 

[D-4297]

Using the Sinclair mandrel die , and was having a similar problem , till I installed a rubber "O"-ring under the Die , allowing it to "float" a little in the press . Don't tighten it to crush , lock-up . Tighten to contact with the "O"-ring , and about a quarter turn more . Fixed my problem .

 

[NorCalMikie]

Keep it simple. What does your target tell you?

 

[Intheshop]

Annealing? How many firings on the brass.

 

[fatelvis]

At what point on the cases are you measuring for runout? Could it be that the necks on your 308 need to be turned?

 

[Straightshooter1]

I use it on .223 lake city brass,get very if any runout.
With .308 lapua brass .004 runout?
I'm not turning necks,I just use them for consistent neck tension

The variance in neck thickness will contribute the neck's runout reading when just a mandrel is run through the neck. The inside surface will tend to conform to the mandrel and the variance in neck thickness will move to the outside where the measurement is being taken. So, adding this variance to whatever runout the neck may have in relation to the case body, the amount is more than if the measurement was taken on the inside of the neck. And depending where the thickness variations are will produce various run out readings that just really don't give you a good idea of what your run out really is unless you're measuring from the inside of the neck. If the necks are turned, then one can rely on an outside measurement.

 

[T-shooter]

The variance in neck thickness will contribute the neck's runout reading when just a mandrel is run through the neck. The inside surface will tend to conform to the mandrel and the variance in neck thickness will move to the outside where the measurement is being taken. So, adding this variance to whatever runout the neck may have in relation to the case body, the amount is more than if the measurement was taken on the inside of the neck. And depending where the thickness variations are will produce various run out readings that just really don't give you a good idea of what your run out really is unless you're measuring from the inside of the neck. If the necks are turned, then one can rely on an outside measurement.


View attachment 1157548

I see one potential problem with your setup in the picture. I hope I'm wrong. I see you have your Sinclair sitting on what appears to be a mat or pad that looks as if it may not be hard, and the inside indicator is not connected to the Sinclair base. Any flex will produce a false reading between the two. I do like the idea and thought about drilling and mounting the dial indicator post towards the right side and figure out a way to mount the inside indicator solidly on the Sinclair base on the left side.

 

[Straightshooter1]

I see one potential problem with your setup in the picture. I hope I'm wrong. I see you have your Sinclair sitting on what appears to be a mat or pad that looks as if it may not be hard, and the inside indicator is not connected to the Sinclair base. Any flex will produce a false reading between the two. I do like the idea and thought about drilling and mounting the dial indicator post towards the right side and figure out a way to mount the inside indicator solidly on the Sinclair base on the left side.

Yes, the Sinclair is sitting on a small mat/pad, a very thin anti-skid mat (so that there the Sinclair wouldn't slide around on the desk top). There's VERY little give in the mat, which the relatively large flat base helps with, that any measurable flex is so small it's inconsequential (like something less than .0001).

And yeah, that's a good idea, finding a way to mount that indicator solidly to the Sinclair base. I'll have to give that some further thought on just how to execute that. Being able to do so would surely make it easier to set up.