Hello furbman.

I could be becouse of the barrel on your rifle or a list of many differant things, BUT I find that if I am shooting alot that I usually sling at least one or two rounds a box. I dont know if it is becouse I get too relaxed, or if I just pull the trigger.

I am not the best shot in the world, But I am a pretty good shot. Just becouse I have hunted my whole life, and am an active shooter.
The fifteen minutes might give you a chance to calm down and refocas on what you are doing on top of letting you rifle cool down.

Hell I dont know just a thought.
Hunter338