As Ben said Sinclair tools are very good products.
I have been turning necks for 10 years for my ppc and 6br rigs, with lapua and sako brass.
A gen rule of thumb for turning necks is to allow a tight fit in custom chambers that range from .260 to .263, I have rarley taken brass off good lapua cases for factory rigs, as it increases the neck tolerance. Factory chambers will range from -.270 to .272, and only requires what refered to as a dusting or uniform the nect thickness for uniform neck tension depending on what gun.
The idea being to have min neck tension and max tolerance to retain a tight neck, for min catridge expansion which equals better accuaracy down range.
You will need to fireform, meassure than perform your neck turning, to suit you chamber, and neck die. For custom rigs you can do this in 2 steps , and take soem off after making your 220 into a 6mm-220
15 years ago when I started shooting BR I was taught by many helpful guys in my local area, some that still hold records, I wont mention names, however I would be glad to pass on the knowledge that was given , and shown to me.
I should add neck turning uniforms the neck, metal so neck tension will be uniform when holding the projectile. Also can uniform the wieght of the case as this is where most where inperfections are. I say CAn because some cases are pretty good to start with such as Norma and Lapua.
Please contact me if you have any questions
PM send.
