I have a 375 RUM that will group under 1/2 inch at 100 yards off the bench out of a led sled. I took it to a 400 yard range and it would group under 4 inches off the roof of my pickup but it was 9 inches lower then I thought it should be. When I got home I shot it off the bench again and it was right on. I thought this was odd so I shot it off the bench holding it and I was 4 inches low, so I tried it off my sticks and it went in the same hole as out off the sled. Then I shot it off hand a few times and had a 3 inch group 1 to 4 inches low. I talked to the smith that built the gun and he and I think that when the gun is solid the muzzle rises before the bullet leaves the muzzle then off hand it can come back thus hitting lower. I was wandering if anyone has a solution to this I really do not like breaks as I do not want to hurt anyone hearing. I am trying to think of a way to hold the rifle more consistent for hunting or weighing the rifle down a bit to reduce muzzle jump. I do not no if they port rifles and if so if that would help muzzle jump without increasing noise. Any insight would be helpful.