Let’s argue about BC’s. I sent some of our 7mm 200 grain ULD RBBT bullets to Bryan Litz for BC testing. He got .74 – this is a huge difference between the .9 many people use to get their drops to match. For the longest time I’ve been trying to figure out why such a big difference. At first I thought it might be because Bryan tested these bullets with a 284 at about 2500 fps and a 9 twist barrel possibly causing the bullet to not stabilize for a while which would lower the measured BC. Bryan said that they were stabilizing just fine though. When I first got my 7mm AM, I zeroed it in at 100, running them at 3250 fps, I plugged in .9 and hit my 1000 yard target about 5” low 3 times. This seemed to confirm the .9 bc. Not long after, I shot at a coyote at 2002 yards and missed left by six inches. Drop looked dead on. I used .9 to get the drop. When people would email me asking for the BC of this bullet, I’d say “Myself along with many of my customers plug in .9 to get the drops to match. However, Bryan Litz from Berger and Applied Ballistics tested them and got .74 – I’m not sure why such a big difference…” or something like that. I’ve never had anyone email back and say .9 didn’t work… and no one said .74 worked either. The difference still bugged me (still bugs me). I think there is an honest explanation. Trying to figure out why, I checked and re-checked everything. I noticed that I left the default scope height of 1.5” on the ballistic calculator (jbm’s) My actual scope height is 2.375 measured from centerline of bore to centerline of scope. After I made that adjustment…. the numbers all changed. I haven’t gone out and tested long range since but the numbers seemed to match with the 5” low hits I was getting at 1000. Last weekend I went out and shot my most consistent load over a chrony at 10 feet and 888 feet. 3 shots each. The ES of this load runs about 9. Here’s the data (averages of 3 shots) Near Velocity: 3300 Far Velocity: 2956 Chrono Separation: 878 ft Temp: 48 Humidity 28.5 % Pressure 25.08 (uncorrected) Altitude 5127 I plugged it into JBM’s “Ballistic Coefficient – Velocity” calculator and got a g7 bc of .740 Why are some people using .9 and hitting targets long range and the measured BC is .74 as per Bryan Litz and myself?I finally think I have a fairly good explanation and I’ll try to explain this later after I’ve shot 1000+ yards with my new numbers. In the mean time,…. does anyone have any input on this? Why such a big difference? Byan, Kirby, Dick, Len, James, Don, ????? anyone?