Sorry for the lack of info.

I was shooting a DISC rifle with 100gr T7 shooting a powerbelt 245gr bullet. I did have the gun loaded...in fact I found the bullet in tact on the driveway about 20-30 feet from the gun.

It was in the middle of my session. I shot about 12 times and I cleaned the gun after about six shots. It only happened 1 time. I am thinking it was a dud pellet.