I have had this 209x50 for about 7 years and have shot a lot of deer and paper with no problems. Today I shot it to check it out after the kids used it for youth season (two shots to deer) and out of 5 shots 2 were on the money and 3 were about 6" low. The three that were low were about a 1 1/2" group same as it always shoots. Same powder, bullet,primer and cleaning. Why the poor grouping. Dismounted scope to check screws under scope and all is good. Remounted scope shoot 3 more same thing. this time two bullseyes and one 6" low. Any help guys. thanks