Wow, neat rifle! I like it as is. Love the wood. With modern powder and components the .458 winchester magnum is a super cartridge. I would love to have a double in that caliber. Anywhere you go that has dangerous game will probably have ammo for your rifle. Thats why I hunt with a lott. Nice feature if you ask me. If it shoots good as is, I would NOT rebore to another caliber. If it aint broke, dont fix it. As stated, might be a bitch to get it regulated with the new cartridge. Conratulations on a fine rifle aquisition.