I use a 30-06 with the euro tubes, and a slimline nib, with either the euro or the slimline cap. An unfired 30-06 is .3337 in outer diameter at the neck, a fired one is .3390. A standard slimline nib is .3000 and a euro .3572 , which is a noticeable step from the cartridge neck. the Slimline nib is a nice smooth fit with no noticeable shoulder. I drill the casing held in my scroll chuck from the inside, so that the (almost always) offcenter firing pin dent in the primer don't throw the hole off. If you plan to use the euro cap with the center band, you will need to turn the bottom rim of the case from .4650 to .4000 to fit inside the center band. Buff the brass and remove all scratches at this point, cause you don't wanna do it later with the nib installed. Then press the nib onto the bare euro lower tube and fill the top end with play dough, base wax or whatever and insert it into the casing. I use the syringes of 5 min epoxy with the little premixer tubes to inject a good shot of epoxy through the hole in the base, into the casing around the tube, then stand it up in a clamp and center the nib on the shell neck. Thick CA will work too, but it's more expensive and harder to clean off. The top end of the tube will enter the drilled hole in the base of the shell just enough to center it. After it dries clean it up, blow out the play dough with compressed air, press in the transmission, and add your cap assy of choice.
Admittedly, these don't have the "gee whiz" factor of the ones with the drilled bullets, but they are much faster to crank out and if fitted and polished nicely look quite professional. I prefer to just renwax mine and allow them to acquire a natural patina, but they could be clear powder coated just before assembly easily enough.
