It's almost absurdly easy.
The reamer is a "Tree" reamer with a max diameter the same size or smaller than the caliber bullet I am trying to form. I'll use the .510" as the example. You can buy a metric 13mm (0.5118" max diameter) Tree-form reamer for about $13 +S&H, but I used a 1/2" one (0.500"). (Here's a 3/8" one
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=290014994025)
I start with a 1" billet of 12L14 or 4140, (or what ever you want), about 4" long. I drill a hole completely through it's center using a drill diameter equal to the size of the meplat I want on the finished bullet. No smaller than 0.125" for the .510" bullets.
Once the through-hole is drilled, I insert the tree-form reamer in my tool-holder on my lathe and use as if I was drilling a hole. At first, the going is pretty good, but as more of the reamer is actually cutting, I am reduced to advancing the reamer only approximately 0.050" to 0.100" before retracting it and removing chips. I continue advancig the reamer to a depth appropriate for the length of bullet I intend to make.
Now a 0.500" reamer, won't make a die suitable for swaging a 0.510" bullet. That's why the reamer is in the tool holder on the saddle instead of in the tailstock. Using the controls on the saddle, I move the reamer "in" (toward my bellybutton) the appropriate amount to ream the proper final diameter.
These reamers leave a very good finish, but I still polish the inside with a "bullet tip" rubber abrasive, and finish with crocus paper.At this point I reduce the OD of the die to 7/8" (if you've got 7/8" stock, this step is avoided), and then cut the 7/8x14 threads that fit the standard handloading press.
I recently got an oven in which I can heat treat metal, but I have yet to use it to heat treat these dies. Even 12L15 is going to last for
several hundred bullets before it starts wearing enough to even measure. Even then, the Lee sizing die, (see next step), will take care of several thousandths 'growth' before a new die would need to be cut.
That's all for making the dies.
I then simply screw the die into the press, assemble the jacket and core, lube to the exterior of the jacket, and swage the bullet. When the bullet is fully formed, I use the 1/8" drill rod to tap the bullet out of the die.
Because I want the final size to be determined by 'squeezing' instead of 'filling out', my swaging die drops a bullet a bit larger than what I want as a finished size. I then run the bullet through a Lee sizing die, (squeezing it down), and it pops out the exact size I want.
Of course the Tree-form reamer has the profile I want for my bullets, and tree-form reamers come in a variety of "normal" diameters like 1/4" (useful for .257 to probably .277 caliber), 3/8" (useful for .375 to probably .425 caliber), plus 5,6,7, 8, 9, 10, 11, 12, and 13 mm, etc. There are some other reamer forms like "round point" that might produce an interesting bullet form. If you want some other form, you'll have to have a custom reamer cut. I think PTG (Pacific Tool and Gauge) will do it for something over $100.
Paul
PS - While it wouldn't be my first choice, I think the reaming could be accomplished with a good drill press and a precision vice - one in which you could control the postioning with 0.001" precision. I would assume if you were going to use a drill press it would be because you didn't have a lathe. That being the case, cutting the threads would need to be accomplished with 7/8x14 thread-cutting die. OR... You could start with a prethreaded die blank (available from Midway USA for $25
http://www.midwayusa.com/viewproduct/?productnumber=512398) held in the vice and the reamer in the drill chuck.
Paul