run out question

[chaneylake]

I just started using my Sinclair concentric gauge.

my question is this - - do I reset digital dial to "zero" for each cartridge or do I set "zero" on 1st cartridge and check from there

#2 - how far from the tip of bullet do I set up the dial indicator, Paul Jones .40 cal bullet, 421.7 grains, as cast, pan lubed

[Lumpy Grits]

Don't worry about "0".
All you care about, is how much the needle moves when you rotate the round 1 full turn.
I set the indicator on the bullets bore-riding section flat, towards but not on the radius.
Gary

[chaneylake]

this is what I got when I set 1st cartridge on "zero" and went through 50 cart.

[Dave Roelle]

check the wall thickness about midway in the bullet bearing section of the case---------you might be surprised how much variablity exists there---coule easily be 0.001 of the total run-out you show

also check a sized but unloaded case on the od -----i found variability there due to a shell holder not well centered

after you have those two contributors to run-out nailed down start working on the degree of expansion of the case mouth-----------bullets have to have a good chance to "start straight" in the case to end up as close to 0 runout as possible

current wisdom indicates less than 0.002 TIR to get match accuracy

the numbers look pretty good except those -004's and 0.005's

i have had lube buildup in the seating punch cause difficulties if i get sloppy with the lube

Dave

[Lumpy Grits]

All you care about is what the round you are checking shows.
X2 on case wall thickness.........
Why was #28, & #49 @ .0045? Was that the T.I.R?
Gary

[Old Jim]

Save the ones that indicate more run-out than you want and use them as foulers .

[Lumpy Grits]

Run'em up in the die again.
Lower the ram and turn the cart. 180* and seat again.......
That should take care of it.
Gary

[chaneylake]

ok, same 50 shells, this time as I put each cartridge onto the base system, I then hit "zero" on the dial indicator for each individual cartridge

[Lumpy Grits]

GTG in anybodys book, there.......
Gary

[Dave Roelle]

well there ya go