I just got an Ohler 35 triple skyscreen chrony and then went out and shot through it. I shot 5 shots through it at 3 feet away from the middle skyscreen. I got an average of 2701 fps with my 7mm rem mag and 175gr. Sierra Matchking. I then moved it out to 53 feet away and shot through it 5 more times. It gave me an average of 2666. I ran these numbers through the JBM Calculations progam to get the actual BC. It gave me .466 It has a published BC of .608. I tried both of these numbers with the muzzle velocity of 2701 and it gives me TOTALLY wrong drop charts! I went out and shot the other day and the actual impact is WAY different than ANY drop chart I can make. WHAT IS GOING WRONG? Any ideas are greatly appreciated.