i just got my 6-284 build 3 weeks ago. (its now getting camoed) but i went with a 27" 8 twist. I did the basic barrel break in. I was shooting 107SMK with H1000 I loaded 15 rounds with 43.5gr of H1000 bullet kissin the lands and i was averaging 3173fps. I was at the bottom of what the book recommends. I wouldnt recommend anytrhing over 28". I researched, researched, and researched some more before i invested. From what i found 28" is optimal (mostly bench shooters giving me info). Anything longer is a waste. I wouldnt go any shorter then 26" either but to each their own.