If going 221 FB, consider the 20 Vartarg, also. Everyone that I know that has one is absolutely in love with it! Higher bc than 22 caliber bullets extends the range a tad, they say.
I have had a couple of 221's, one on a set back 223 Rem 700 varmint, and another on a 20" Thompson Contender. I shot the 40 at 3600. Also had a short and long range load for the 50g Speer TNT using AA1680.
Consider feeding issues associated with a Rem 700....it ain't gonna work without considerable work and expense. A single stack CZ or Tikka maybe a better option, right out of gate.
My 221 FB's were p. dog and squirrel rifles.
I use a set of form dies made by Paul Bike, they are fabulous to say the least. Harbor freight makes a nice litte cut off saw for around $59.
If you go the 221 FB from Lake City brass, it would be prudent to try and buy new Lake City brass OR buy a Redding Small base sizer for the 223 before you ever get started. Often, those chambers in the AR's are beyond huge, especially if the brass is fired in a SAW.
Be aware of the fact that the brass retains a memory of the chamber it was first fired in. You size the brass down, it has a "spring back". Often, if the chambers are huge, it will "Normalize" over time, trying to spring back out....how much is a guess. I have ran into this a couple of times in a couple of different calibers other than Lake City brass.
Often, custom 221 FB reamers are designed tight in the web, I got busted by this also. I want the reamer print to be .003 larger in the web than the LC brass I am using.
If you like making cheap brass, consider the 222 Remington also, they feed from a rem 700 action with ease. In 20 caliber, the 20 bobcat is off the 222 brass if my memory is right.
As far as neck turning, I use a K&M in a slow adjustable speed 1/2" drill, and can turn 6 cases per minute...nice Winter project for a couple of thousand rounds. Have a TV in the garage set on Fox News, the more upset you get at the liberals, the faster you turn the necks.
I set the speed of the drill with the little wheel in the trigger, mount the drill in a large bench vise, just feed the cases on by hand...easy peasy. The slow speed of the 1/2" drill is much better than a drill press unless you can find a drill press that goes down to 70 rpm and most are 3x that amount. Gauling of the mandrels is an issue.
I am making the 6 XC cases from new Lake City 308 brass now, stuff is tough as nails. I tested the accuracy of formed cases and it was sub to 1/4" groups.
These kind of wild cat projects are a lot of fun, if you like this kinda tinkering fun. Most would consider it like sitting on the front porch steps killing ants with a hammer. I say, pass the sugar water.