It is possible that part of the powder was contaminated. You will know more if when you clean the rifle the barrel has a lot of unburned or chunk powder in it....

And that is why a lot of us unload every night and then clean them. I know tonight when I came out of the woods I thought... should I leave the charge or shoot it and clean it... Well it did not take much to clean have only one round put through it. I clean them every night.