Fred'
i hope what i say below sounds reasonable. it may provide an alternative to your customizing by way of re-boring.
my suggestion, since i am a bolt action fan more than a Handi' fan when it comes to calibers over .223, is to buy a Remington Model 700 VLS if you want accuracy, enough weight (9+lbs) to Easily handle recoil, and a reasonable choice of calibers. you'll get a laminated stock, a heavy 26" barrel, an adjustable trigger, and calibers that will do long-range varmint, deer, and elk duty. i see it as a rifle you won't have to customize, because of its excellent accuracy reputation. it is a Great platform to build on; but there really isn't much needed unless you get into very stiff competition.
as you know, you won't get the light-weight utility and portability that we get with a Handi'. you'll never find a better, more portable rifle for under $300, in my opinion, than a Handi'.
by the way, i say long-range elk capability -- since the rifle only goes up to .308 caliber -- because of the use of handloads, high-energy factory loads, and its long barrel. i figure that reloader 15 would move a 165 gr' bullet out of a decent 26" barrel at over 2825 fps with no pressure problems whatsoever.
blessings upon you,
ss'