I just downloaded the Shooter program for my phone and didn't know if I should use the G1 or G7 BC. I'm shooting a .308 168gr SMK. The G7 seems closer to what I've seen in the field shooting, G1 seems to be about 1.5 MOA off.
The G7 is usually closer at the longer distances. I feel either will work for your 308 if you have solid velocity input along with accurate field conditions. Watch shooting too close to the chronograph. I keep em 18' from the muzzle so the blast does not interfear. Also remember many cheaper chrono's will lie. I would use the G7 and check the drops at 300, 500, 700 and 1000 on the same day and range if possible. Then use the velocity that puts them all spot on to .25 moa average from center group.
I have experienced no difference between the two using my 6.5x284 with 140 VLDs out to 1000 yards. My ballistic calculator shows about a 1-2" difference in elevation at 900 yards and this appears consistent with actual impact points. I haven't tested past 1000 yards, but my calculator begins to show more significant differences, with less correction using G7. The ballistic curves in Bryan's book appears to bear this out as well.
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