I have only used one, a Mcgowan 6mmbr 1:8. With 95 grain Berger VLDs jumped .030 and Varget, I have yet to find a load that shoots over .5" at 100 yards. One ragged hole groups are the norm. With 70g tnt, 105g a-max and 75 and 87 v-max bullets, the best loads will go in the .4s and the worst closer to an inch.