Can powder deteriorate over time? About two and a half years ago I load some .280 Rem. 160 gr. Accubonds with H4831. I loaded to achieve 2900 fps which the book said was max. Last month I bought a Chrony beta. The Chrony says that my rounds were traveling a lot less than 2900. I carefully load up, without pressure signs, to 2900. I then pulled the bullets from the rounds originally loaded two years ago and added powder. Same bullet, same powder (in fact it is from the same can), same case, the only difference in the two loads is the primers (original rounds are Fed. 110, newest CCI Long Rifle). The pulled and reloaded rounds are 200-250 fps slower. Day time temperature was about 15 degrees cooler today on the pulled and reloaded than when I fired the others a month ago. What’s going on?