No, George, you wouldn't be wasting your time. Couple of things to consider, though. M12 seems to be about the smallest you can use for cap/barrel threading (some use M14). The standard M12 threading is (if memory serves) 12x1.25, the second number being the distance between sequential 'peaks' of the thread. It is also the height, or distance from a 'peak' to a 'valley' of the thread. So an M12 thread would leave 9.5mm of core material, being 12mm less 2 by 1.25mm. Not bad until you consider that the section will be threaded into the barrel at this same point. (Barrel has a male thread for the cap, a female thread for the section.). Assuming you use a standard M6 tap for the section, you're losing (6mm plus 2x1mm) 8mm from your core. So you're left with a barrel wall thickness of (1.5mm divided by 2) 0.75mm. Not much!
Most kitless folk therefore opt to use an extra fine (but still single-start) M12 die, M12 x0.75. They're not too expensive (like here) and they allow better strength because you lose less core material. As an added benefit the threads look less 'industrial.
