a few fs issues ago john alexander discussed using the lee collet neck sizer...and adjusting it for inside diameter ....by raising and lowering it in a press. GOTCH HIM ! ...well, partially ... maybe ...
1) let us dream for a minute that squeezing the outside of the case neck to a given diameter.....either with the lee collet, or the exquisite redding s type bushing dies .... will produce the desired inside diameter ....
FATIGUE CITY! even john confesses that this requires neck thickness machining to a high ( low? ... thirty years a machinist and i still can't get that straight ... ) ... tolerance. lots of very drugant work ... i had a buddy who neck turned all his thousands of rounds of p.dog ammo. ( side note: yep his 22-250 shot 1/4 groups. )
2) if one were to use the collet die correctly ....one would save a lot of hassle ...by not turning necks....and would also get consistant ENOUGH neck sizing. the correct way ....is to mash the brass against the mandrel firmly....this makes the inside diameter the same ..... and the adjustment is accomplished by using different diameters of mandrel rods.
a good starting diameter for castered bullets is 0.002 under bullet diameter. springback will be about 0.002 so this will give about a slide fit.
you are now probably wondering just where you are going to get an assortment of mandrel diameters .... hey, i am just the messenger ....( heh heh ) ...but if i had my machine shop wired ...i would turn them out between centers on my hand lathe...so maybe mr. lathesmith would do the same if asked ...he advertizes here ... i have used as material both stressproof ... and fatigueproof ...both slightly harder than coldrolled ...for expanding rods ...lasted for 30 years so far ... fatigueproof is available in small quantity from brownells. it also makes a great bushing for refacing your bolt after shooting old cases and pitting up your perfectly good rifle bolt (g ).
while we are close to the subject .... i should mention that neck tension is not nearly as important to accuracy as is commonly reported ...it is BULLET CENTERING WHEN CHAMBERED that is important.
neck tension...and crimping ... is important ...to keeping the bullet in the case ... in revolvers....and tube magazines ...etc. but accuracy wise, no big difference ..that is because when fired, the brass neck is blown away from the massive bullet first thing... and leaves that putty-like lead bullet just hanging in mid-air... geeze no wonder i have to move those bean cans closer ...
speaking of fatigue, i b ken