I have been trying to issolate inconsistancy concerning a bull barreled AR 223. Groups were shifting and formula for tighter groups seemed to change per each range visit. I replace older leuplod with NF to rule out scope being problem. The NF came off my bolt gun and I KNOW IT IS OK. So far I have determined that fouling the barrel seems to initiate a better baseline for comparing the following powder workups. While I was testing loads, I made sure to compare CCI BR primers/powder formula to std CCI SR using same powder/bullet. I discovered that BR primers used over the array of different powder weights, seemed to produce slightly larger groups at 100yds, but both std and BR primer groups stayed in one spot. This results was a bit confusing to me too! I was graduating in 1/2 grain increments from digitial RCBS scale that I had also carefully calibrated.The results, so far, indicates that BR primers used with my bull barrel AR don't preform as well as STD primers. I am still scratching my head over this.
I keep all of my primers in an air tight 50 cal ammo box. So mosture shouldn't be a problem. In can is the decatant stuff. I also have primers dated and use them by older dated ones first.