Every time someone tells me their Mini launches the brass into the hinderworld, I ask them if they had ever taked the gas cylinder apart. The answer is usually "yes". The next question I ask them is if they remembered to reinstall their Gas Block Bushing. That's when the blank look on their faces appears. Without the bushing, they increased the amount of gas to the piston.
I prefer to shoot .223 from my Savage 12FP bolt gun. 5 under a dime at 100 yards. The Colt HBAR gives 1/2 inch groups with iron sights at 100 yards...on a bag of course.