Neck Turning - Mandrel how tight?

[rem40x]

Greetings,
Turning some 6BR Lapua brass and getting too much deviation on sides of neck. I FL resize w/ Redding .269 bushing, then using Sinclair 2000 expansion mandrel, then under a power lathe, attempt to turn to .00105 and getting .00104 to .00110 of some. I think there is too much slop in the cutting mandrel. The brass slides on easily and I can feel a little "give". I'm free floating the cutter in my hands and it takes off brass on the in and out slow pass. Making one pass then checking w/ nk micrometer. Should I polish the expansion mandrel for a tighter fit? The tools are not getting even warm.
Thanks for all the help.
Regards,
Greg

 

[Preacher]

Those are some kinda numbers like gunamonth mentioned, can we assume your pushing the point to more than it's reading ?
Whatever the numbers really are, the mandrel your using to make the cut should be a fairly tight fit, but still be able to turn easy if it's lubed..

 

[JayIdaho]

How are you measuring the wall thickness? IMO, a micrometer is a better tool to use than a dial indicator against a mandrel. I have a number of travel indicators and test indicators, use them frequently, but prefer a mic for neck wall measurements.
Opinons vary.....

 

[rem40x]

sorry, meant to say I have a dial indicator on my cutter for adjustment and measure nk thickness w/ a micrometer. Missed the decimal place cutting for .266 nk so .0105 per side.
The brass turns easily w/o being lubed so I think I'll turn down the expander.
Appreciate the suggestions.
Regards,
Greg

 

[rem40x]

That was it. I had a good friend turn down a .257 mandrel to the right "tight" size and now it works perfectly. No slop and consistent. Thanks for all the help.
Regards,
Greg