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Posted: 6/8/2026 2:07:27 PM EDT
| Shooting an 18" 5.56 gas gun today. 77gr TMKs out to 600. For some reason the come ups from geoballistics are about 1 mil low from 300 to 600. I verified zero and velocity. It's been spot on in the past. I was able to make hits by adding 1 mil to every solution it fed me. What could cause this? |
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| I considered this, but my zero at 100 is still good. If something is loose, it would show up there. I just remembered I recently updated my bullet BC data from G1 data to G7. Since that's the only change I made recently, it must be that. Why would that have such an effect, if the new G7 data I entered was supposedly correct? |
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| I switched rear bag Brands recently and I realized this was the first time with that bag for these two rifles. I wonder if that's it. But if the bag was causing the 1 mil error, I would think that would show up during the zero verification, and it didn't. MY zero was spot on with both rifles. |
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| I noticed one of my elevation knob set screws was loose. (Mk5hd) The other was tight. I tightened it and the issue seems to have resolved. I'm not sure if that was the cause, but I have a slightly different issue now. I can make hits at 300 and 600 yards fairly easy on a 6" plate, but 400 and 500 are really giving me trouble. I'm still trying to figure out how to fine tune the GB ap data. |
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Well that's cool. Glad it was something simple! I'll be using geoballistics next weekend and a midrange shooting class that goes out to about 500-600 yards. I took a similar class last year with my 18" MK12ish rifle and was making good hits, so we'll see how the 14.5 does this time around. |