Wildcat/brassforming/fun project question

I like the look of the 6br as a varmint round. But why not save the hassle on a fully fledged build and just get a 243. But then I'd like less capacity than the 243.
So just for interests sake. Could you just get a 243, set the barrel back 2-300 thou say without rechambering and then turn 2-300 thou off the bottom of the FL die. Obviously would need to neck turn, trim and anneal but I thought it could be a fun project. You could seat the long projectiles out a mile and you'd be burning less powder. My question is , would the taper of the brass be an issue or is it feasible?

@Tuckerbox

The benchrest boys will tell you short and fat is where it's at.

Can't see why your wildcat won't work.

Give it a go and let us know how you get on.

Cheers
Pete

Yeah my 7 Saum is awesome. Short and fat chode cartridges get me off . Especially if they have a big high bc projo seated right out.

Better to chop the chamber off and re-chamber to 6mmBR great calibre had 3 at one time now down to 1 a Ruger No1 25" True Flite barrel shoot 87gr Vmax with 31.0grs 2208 1/2 MOA
when I do it properly, barrel will outlast a .243 by about 3000 rounds, Now shooting cast bullets in it for bunny hunting will last forever.