Shortening the length of a pencil-barrel MIni has been a longstanding method of increasing accuracy. Unfortunately, doing so to the already short Mini barrel reduces the effective range of the firearm.
If one has a pencil barrel with a (former) user-damaged muzzle, then either re-crown the muzzle, or have it slightly counterbored by a gunsmith. In any event, install an AccuStrut, which will take a huge amount of barrel whip out of the equation. Install the barreled action into a tight-fiting syn stock, and you are GTG. OR, carefully bed your barreled action into your wooden stock.
In a lot of ways, accurizing the Mini as far as the stock fit is like accurizing the M-14/M1A.
Most savvy Mini owners buy a port kit with a number of different-sized gas ports included. Ruger originally supplied the Mini with a relatively HUGE gas port, which ensured VERY positive ejection, for reliability's sake. Also launched the brass into orbit.
Most folks find that they can reduce the gas volume released by the replacable gas port. How small a gas port is up to the user, but I would caution against using the two smallest ports if cold weather ops are anticipated. Ammo is a bit less energetic in cold weather, so test your Mini with its new gas port kit in the coldest temps available.
The advantage in using a smaller gas port is that the recoil is less violent, and that the brass is not ejected into the next county. Time-onto-target is reduced, and the rifle is not internally battered, not that this seems much of a problem.
Once the user has replaced the gas port, and has the top and bottom clamps almost tight, the user will notice there is a fair amount of rotation about the axis of the barrel. Even things up so that the clamps are evenly spaced, side-to side, and they are an equal distance from the stock. Tighten the screws with uniform force.