If you can buy a good quality, good condition 7x57 bolt for the same money as a new Handi I say buy it!! If not, another option would be the 7mm-08 Handi. I have a shortened .280 Handi barrel (19") and it is a great deer, moose and black bear gun. I as you, like the .284 and have a 7x57 Handi and love it, it is a real tackdriver and more than capable for deer hunting to 250-300 yards. The accuracy is up to me not the gun, since the gun is easily up to the task. Tough decision you have there, good luck....<><.... :grin:
1) used bolt in 7x57
2) Handi in .280
3) Handi in 7mm-08
4) what to do, what to do! List the pro's and cons, expense, recoil, requirements for new caliber (what your going to use it for), bullet weight and rate of twist, availability of brass and loaded ammo, and last but not least, WHAT YOU WANT!!!