5r rifling is certainly the way to go. opposing groove and lands means less deformation, as does the canted lands. cleans easily and great velocities out of both of my 5r border tubes.
as to the quality of border barrels work, i have 4 of their barrels. 2 of them are the archer barrels, built on rpa quadlites by rpa. accuracy is fantastic and both have taken a lot of silverware home this year.
the other 2 are cut-rifled 5r tubes in 6.5 on my f-class rifles. one is an accuracy international that borders re-barrelled for me and it is wicked(And is for sale if anyone is interested). best group this year is 1" for 5 shots at 500yards using a bipod!!!! the other one is on my 6.5-284 full race f-class gun that borders built for me on a quadlock action as shown below. workmanship and accuracy is as good as anything out there imho. colour scheme is optional....
geoff and the boys all shoot competitively and geoff's knowledge on barrels and ballistics is mind boggling. they come thoroughly reccomended