I have built 2 Rem.700s. One in 375 RUM. the other in 416 Rigby. I had put a Seekins detachable magazine on both and they wouldn't feed very well so I sent them to Wyatts to have Kevin put one of his magazines in them. When they came back they fed great but they both shoot vertical strings. I talked to Kevin and the smith that had built the guns and they are both stumped. With out the magazines in the guns they both shoot 3/4" groups, with the magazines in they shoot vertical 2 1/2" to 5 1/2". It has something to do with the magazines. Does anyone have any experience with this problem?