I was shooting over the last few daysto check zero for a match and the temperature was up from 70 deg F to 91 deg F. the temperatures will get a good deal warmer yet like well over 100. I noticed that the average speed of the load went up by 14fps and the SD went from 4.1 to 10.3 fps. Groups were still great a little over .4 for both days. sample size was 20 shot groups.
Rifle is a .260 rem bolt gun using lapua brass, Berger 140 elite hunter, CCI BR2 primers and H 4350 which is really ADI 2209 an Australian made powder exported to the USA and rebranded. Chrono was Dopler radar, temp measurement was with Kestrel drop.
Question is are shooters adjusting their loads to keep the speed at a set point? At distance 900 plus yards good SD's matter and I was disappointed to see the shift. on previous testing I have found .1 of a grain equals roughly 15 fps so maybe bringing the charge back in warm conditions is a plan???
Rifle is a .260 rem bolt gun using lapua brass, Berger 140 elite hunter, CCI BR2 primers and H 4350 which is really ADI 2209 an Australian made powder exported to the USA and rebranded. Chrono was Dopler radar, temp measurement was with Kestrel drop.
Question is are shooters adjusting their loads to keep the speed at a set point? At distance 900 plus yards good SD's matter and I was disappointed to see the shift. on previous testing I have found .1 of a grain equals roughly 15 fps so maybe bringing the charge back in warm conditions is a plan???