I read in a book where the author said he had a load that was accurate if you shoot it within a few days. But it sets for a while, the accuracy is unreliable. I have experienced this, but decided it might be temperature and switched my load. But I have suspected this with other loads. I recently tried to pull a bullet out of a cartridge loaded a few years ago. It would not come out. I had to give up. I could probably shoot it, but the neck tension must be incredible. Any input on this phenomena is much appreciated. I have loaded enough 300 WM to last for years of hunting. I hope I did not make a mistake.