Actually this is very common on the new and un-improved Mini. Some have fixed this problem by loosening the gas block screws, torquing them to 36 inch pounds with equal spacing between halves. Others have had to send it back to Ruger for rear site replacement.
You can go here to learn more about what makes the Mini tick.
http://charlie6.org/c6forum/viewforum.php?f=6

Give a man a fish and he eats for a day. Give a man a welfare check, a forty ounce malt liquor, a crack pipe, an Obama phone, free health insurance. and some Air Jordan's and he votes Democrat for a lifetime.