This is what I did to tame down my Mini 14. Use an allen key (the individual right angle ones you can get as a set at the tool store) to loosen the 4 screws, they will be tight because the factory stakes the threads. Take out the factory bushing and use a digital caliper to measure the thousands of an inch length of the new one to the old one (a digital caliper is like $15 at harbor freight). You don't want the new bushing to be longer than the old one, if it is then file or grind it down slightly, or else it will get jammed into the barrel when you tighten the gas block down. The gas bushing sits in a recess in the barrel, and also a recess in the gas port pipe that goes to the op rod. In this stolen pic the arrow is what you are replacing:
Reassemble the gas block, put blue thread locker on the bolts, and tighten the gas block so the gap between the upper and lower halves is even on both sides. The gas port pipe should have a slight wiggle play when everything is snug, if it doesn't then the gas bushing is probably still too long and getting jammed into the barrel. A good way to not over torque the bolts is to tighten them using the long end of the allen key in the bolt and short end as the handle and snug them up good, you won't break them this way.
Get a set of 1911 pistol recoil buffers and put one around the base of the op rod to dampen the impact when the op rod slams forward, and another around the recoil spring guide rod to buffer when the op rod slams into the receiver. These stolen pics will explain:
Get a bunch of them, as they get beaten up after 500-1000 rounds. Check to make sure that the buffer isn't too thick to prevent the bolt locking open on an empty mag.
These two mods have cut the recoil by probably 30% and the brass only goes 20 feet instead of 40 feet. You might still get some dings in the brass when it gets ejected and spins around and strikes the op rod, mini's are not kind to brass.