would it be possible

[tiny]

to make a self centering hand held cutter. that would take a plain base bullet an trim it so a gas check would fit on it. in different calibers. so with one mold you could have either plain base or gas check . tiny

[243winxb]

Sure, with the right tooling. Or swage it like here. http://www.thehighroad.org/showthread.php?t=180828

[Leftoverdj]

to make a self centering hand held cutter. that would take a plain base bullet an trim it so a gas check would fit on it. in different calibers. so with one mold you could have either plain base or gas check . tiny

Anything is possible, but many things are not worth the trouble.

You are essentially talking about lathe turning. That's sometimes done for experimental purposes or to make a handful of hunting bullets, but I don't see a handpowered gadget as practical for any sizeable quantity.

[yondering]

That sounds simple enough to me. You might want a non-cutting sleeve section that would fit the outside of the boolit, to keep the check portion centered.

You might PM Buckshot, I've heard he can make stuff like that.

[leftiye]

Not hand held, but you can put your plain base boolits in a collet in a lathe and turn down the bottom band to accept a gas check. Yondering's idea could possibly be done with a tube with a cutter in the tube. You'd have to find a way to turn the boolit in the tube without damaging it. Possibly by hand. Or maybe with an RCBS boolit puller collet.

[243winxb]

Take the center pin out of an RBCS chamfering tool, cut a bevel to start the GC on to the bullet, then swage in the lube/sizer. The center pin might be modified so it could be used as a cutting stop. Problem would be working with the hardened metal. http://www.sinclairintl.com/images/large/63-09349-l.jpg