Grinch,a lot of this depends on what a person has to work with,equipment wise. Don't think it can be done without a drill press or lathe.
A lathe that accepts collets is too easy.Just get one that fits the diameter of your bullet and use a threaded "stop" coming in from the backside.Use a small center drill for the hole..... picking it's diameter based on the size of the Torx bit.After drilling replace with the bit and swage to some sort of repeatable depth.
Realizing,you may have to play around with tooling and procedures to minimize error.Which is where most folks are gonna drop the ball.You have to be able to understand stacked tolerance from the standpoint of how you can mitigate it.Easier said than done...... think precision handloading.There's many ways to get from here to there. Exclaiming "my way or the highway" is NOT gonna get you very far. You have to be willing to try different methods,choosing the technique that works best in your application.
I don't have a lathe in the loading room,BUT.... got drill press.Several lathes in the shop however. Basically in a DP( drill press) it amounts to an extremely close fitting "drill guide".Which are used in std fixture design in manufacturing. It's a hardened steel "bushing" that has a hole in it the size of the drill.The fixture can then be made out of practically anything harder than say a pce of pine. In this case,since the product is a bullet.... you have to shape the drill guide to reduce error to zero.....
A quick way would be take a well fitted top punch and use that as the basis for a drill guide.I make "D" reamers to create upper swage dies for nose bumping.So just take that and make the drill guide. What we're trying to achieve error wise is so a blind person can do this( no offence),and not miss a beat. Then it's just a matter of locating the bullet in a "lower" fixture. I'm looking to order another 5C collet holder for the loading room,keeping this tooling away from the shop. Because,"I" like collets..... someone else may approach it differently. Further,I have other plans in the loading process for these collets so it becomes an investment in future work/projects. At some point would like to drop a bullet nose down in a 5C and mill the base,along with some other,not so crazy ideas.
I'll update with pics as the tooling gets streamlined.