I appreciate so much all of what I expect is quality advice. So, what is the best single stage I can buy, and what are the best other components to the process that will allow me to turn out quality precision cartridges? I have had two custom rifles built, one in .300 win mag and one in .300 wsm, and I want to find the most accurate loads for each in various bullet weights. What will allow for precision? I also have purely factory rifles (.243, .308, .270 wsm) for which I also want to find the most accurate loads. I will not be loading for handguns.
A couple of thoughts for you:
Assuming these are bolt action rifles (most likely), then dies and brass processing become more important. Many reloaders do not full length resize the case after every firing, but just re-size the neck using either a bushing next sizer or a Lee collet die (I use Lee). Then re-size case only when empty brass shows some resistance on the bolt when chambering using a “body die” that only touches the shoulder of the case. 300WM headspaces initially off the belt on the head of the cartridge but after 1st firing, can headspace off the shoulder.
A simplified process would look like (starting from fired brass)
1. Deprime case using de-priming die or hand de-primer.
2. Tumble to clean (or maybe just wipe and use a case neck brush if getting started to avoid tumbler cost).
3. If brass chambers easily (no bolt resistance when closing) - use Lee collet die on single stage press (apply 15-20lb pressure on down stroke - this die functions differently than other resizing dies). So need press, collet die and shell holder for this step. Check case length and trim if needed.
4. Prime re-sized case. I use an RCBS hand priming tool.
5. Charge primed case - need powder scale (I use RCBS chargemaster). Also need funnel and a loading block to hold the cases helps. Buy a reloading manual for powder/charge selection and start low and work up slowly.
6. Seat projectile - need a seating die (I use micrometer seating dies from RCBS and Forster).
7. Measure - need bullet comparator set and micrometer to measure correct depth. A friend could help measure the chamber or get data from your builder for a specific projectile.
Later you’ll need to anneal and add a re-sizing step, plus case cleaning and trimming tools, case gauges, etc.
Over a few years, you’ll develop your process and accumulate the tools.
I find it as (or more) rewarding than shooting sometimes!