Re: Sizing 6mm to .22
The first you need to establish is your chamber neck dia.(which your smith should have marked on the side of your barrel) and your choosen neck clearance,between your finished round and your chamber neck dia. I say choosen because you need to know if you want to shoot tight necked rounds(typically .001" to .0015" clearance.) or not. Unless you are shooting a benchrest gun i would not reccomend it. Once you have established this,( i consider .003" to .004" to be good, and remember this is in total not per side.)you're ready for the next step.
For this you will need your dies, a neck expender with .224 mandrel and a neck turning tool with .224 mandrel,micrometre or vernier. K&M make both these turning tools and are excellent quality. The expander mandrel is sized slightly bigger then the turning mandrel to allow for brass springback and a perfect fit. Are you using neck bushing dies or or a chamber type sizing die? either way, If you are using a bushing die, select a bushing that will give you about .002" neck tension( I.D. .002" smaller then bullet diametre.) and size your case,then seat a bullet. If you are using a chamber type die you might find that after sizing th I.D. of your neck may be to tight to seat a bullet, in which case if you expand with your expander mandrel you should have enough tension to hold a bullet in order for you to get a measurement.
Using your micrometre, measure your neck complete with seated bullet, this will be your loaded round dimension,which will be subtracted from your chamber neck diametre according to what clearence you want and the amount of material to be removed during neck turning.
Now before neck turning all cases have to be expanded, so firstly neck size all your cases and then set up your expander and expand all of your cases, a dry powder lubricant is good for this operation. Set up your neck turner as per manufacturers instructions and you are ready to neck turn,after you heve worked out your figures. The K&M neck turner comes with a handy case holder that fits into the standard hexagon of an electric screwdriver, enabling you to turn under power. Now for some figures, hypothetically lets say that our;
1. Chamber neck diametre is .242"
2. loaded round diametre is .248
3. our desired clearence is .004"
4, our bullet diametre is .224"
this means you need to remove .010" in total to give a finished neck diametre of .238" with the seated bullet or a neck wall thickness of .007". Dont be tempted to remove all the material in one hit, do it in three or four passeswith a final fine cut. This is a long and drawn out process which if you are wildcatting should be done and remember it only needs to br done once. I reccomend that combine this with primer pocket uniforming, flash hole de-burring and top quality components, as it would be ashame,after all that turning to, sort of leave it half finished. I, myself perform all these operations on my brass for 243 and my 300WSM, utilising partial neck clean up rather than full neck turning, I used be a bench rest shooter and i used these techniques when converting Lapua 220 russian brass into 6mm PPC and i think its well worth it, even now because i have the upmost confidence in my ammunition. Well, i hope i have covered this process enough to get you on your way,you'll cock up brass you'll get frustrated but you'll be glad when its done,good luck with your new project and please let mr know how its coming on.