Well good luck with your build! The stiller tac 30's are good actions but for the money I feel there are much better ones. They aren't up to modern actions like some listed below. It depends on your price point but can break it down a bit for you.
more budget actions;
- zermatt/bighorn origins (mechanical ejector, controlled round feed, loads of prefits available, swappable bolt heads for caliber family changes). Super smooth actions.
- kelbly atlas tactical action. (Mechanical ejector, incredibly smooth, trigger hanger, wicked customer service, prefit availability)
- defiance tenacity (strong defiance name, rock solid, prefit available, a few options in cuts)
higher end actions;
- bighorn tl3. All the same features
- defiance deviant/ruckus or anti/anti-x. Depending on weight for the build you can choose the deviant/ruckus for a target/tactical build or the anti series for a hunting build
- impact737r/787r has unlimited prefits, incredibly popular, number 1 in prs.
-terminus actions. There entire line up is just good. 60 degree bolt throw though which is faster but heavier lift. Unbelievable service, incredibly smooth, almost feel like they close themselves.
there's a bunch more out there but that's a good start. Figure out your budget and go from there.