Ive posted this before but when the 60 NPTs came out JB had a Juenke Comparator, and he tested a box for concentricity, and sorted them into three piles, good, better, and best. I ran them through my most accurate .223 with a known load and that exactly how they shot. .75 for the best, 1.25 for the 'good'�
Wild guess from a layperson but it might be harder to overcome concentricity issues with two cores...
