Re: 6.5-284 Norma
Oh yeah, huge differences. Barrel making is quite an art form, as well as a science, but basically it comes down to the care/knowledge of the operator. Buttoned barrels are faster and easier to make and can turn out a very fine product. Depends on the maker as to how it's drilled, if it's reamed (not all do this), how well the bore is lubed before drawing the button through, and whether the button is allowed to determine the twist (as most are) or there's a mechanical fix applied to help define the twist. Some will anneal their blanks to soften them before drilling, while others leave the barrels hard throughout the process. All kinds of different ways to skin a cat, if you see what I'm getting at.
Cut rifled barrels are a great deal more labor intensive and take much longer to make. The deliver more uniform twist rates, but again this requires a knowledgable and conscientious operator. Cut barrels generally need to be lapped, where most buttoned barrels don't get this treatment. Adds another little variable to the mix. There's also the question of the barrel steel quality, which the maker generally has little or no control over. He specifies what the material is to be, but it's the smelter who has to keep that correct. There's a whole lot more to it than this, but you get the idea.
Either process can turn out very good barrels, and they can both turn out crap. Stick with the makers who're providing a lot of barrels to the competitive crowd, and you'll likely get a good one. Go to the cheap side and buy a $59 barrel, and you've got . . . a $59 barrel. Don't expect them to shoot the same, 'cause they won't.