AustinMike Posted January 2, 2007 Share Posted January 2, 2007 Sanity check...can the angle of the sun cause errant chrono readings? I got consistently low readings today from my 9mm major load (159 PF) that usually is around 170 PF in the summer. Temp was probably around 60 degrees today, so not too cold. I know temperature can influence the powder burn, but the ammo was taken from a heated environment and not exposed to the cool air for more than 15 minutes before shooting over the chrono. The sun was coming in at about a 45 degree angle, straight into the front of the chrono. Sky screens were used as there were no clouds. I would have liked to have tried taking readings with the chrono perpendicular to the sun, but there was no other choice at this range. I'll have to try and find an opportunity to take a new reading at a different range sometime this winter. Could the angle of sunlight have caused lower than normal readings or is temperature a more likely culprit? Powder was HS-6. I'd hate to have to bump up the charge if I don't have to. Last July, I chrono'd the same load at 172 PF average out of a 10 shot group. I checked this load several times last year (albeit in warmer months) and my lowest reading on record is 168 PF. Quote Link to comment Share on other sites More sharing options...
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