Took my .243 to the indoor range today to try out some new berger bullets which I had just loaded several hours prior. First shot went off with a puff instead of a pow? Pulled the case out and it had several pieces of unburned powder left in it and I have no idea where the bullet ended up but it wasn't on paper. The next 5 went off just fine, what could I have screwed up on during the loading process?