Several have asked whether you should do initial testing with or without the tuner installed. I say, definitely with the tuner installed and set to zero. It can be done either way but why bother and put more rounds than necessary down the tube.
When I chamber a new barrel, I also thread the muzzle for the tuner and conduct initial load testing with the tuner set to 'zero.' It seems a waste of time to do otherwise.
I shoot only short-range group with either my 220Beggs or 6Beggs in a 10.5 pound Hall Sporter. I use either Krieger or Bartlein barrels cut to 22 inches. I know what muzzle velocity to expect and obtain that with whatever powder I'm using at the time. I've used N133, pulldown 8208, H-322, LT-32, Benchmark, H4198 etc. They all work fine in either cartridge; same goes for the 22 and 6PPC. My 220 likes to shoot at 3500 to 3550 and the 6mm at 3330 to 3350 so there is no time wasted testing at any other velocities. Once I reach the desired velocity as shown by the Oehler 35 chronograph, I lock the Jones powder measure at that setting and NEVER change it.
Seating depth? As far as I'm concerned there is only one; JUST OFF THE LANDS. Yep, I don't waste time with anything else. So with that said and accomplished, it leaves me with only one thing to tune; THE TUNER, and it's the easiest thing in the world.
Hope this helps someone.
Later, Gene Beggs