I've had smaller mills and lathes before. Not in a rush to thread and chamber anything I'm going to use. I've had this mill and lathe for 6 years but getting it setup was a 5 year wait.
My previous was a Sherline which I eventually made CNC. Used it to make hundreds of parts for RC planes. "Semi" production and custom motor shafts for the DIY brushless motor builders. Held to .01mm (aka ~.0004"). That was all done with insert tooling.
I'm starting slowly. I've made a bunch of expanders for my pbike257 forming die, delrin bore rider jag adapters and things like that but most of what I make is parts to upgrade the mill and lathe. AFAIK, the best way to know your mill and lathe is to make parts with it and for it with it.
Also with this setup I'm learning to grind, sharpen, maintain and setup HHS tooling. When I get it right it's better than the inserts. As in: roughs faster and finishes better but I have a nice selection of insert tooling if I just need to get something done.
I've gone from everything manual to independent power feed in the lathe, boy did that make a difference in finish. The threading gears just could not match the slow steady pace of a power feed.
I've changed the manual head movement on the pedestal mill to powered head. Installed an air driven tool changer. I started with no DRO, all dials and back lash adaptation to now installing the scales.
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I certainly could make the tools. There are plenty of designs available and it's not "technically" difficult. It would be fairly easy to copy the Brownells design and make the inserts for each barrel diameter.
For making the action wrench, welding is my least skill in metal working. Brazing and torch welding ok but ARC and wire feed? It's been 40 years since metal shop class and I just don't remember any of the welding stuff that wasn't flame based. My biggest issue with welding at the moment is its summer in California and fire danger is serious. Not the welding equipment but an errant spark that could burn down California. I have no place to weld where a spark won't reach dry grass. I was going to "practice" by building up the edge of the bucket on my back hoe/loader. Needs it bad.