AccuStrut makes the SOCOM 16 model of their barrel brace specifically for 16in bbl rifles. I bought one and put it on my 18.5in Mini 14 (yr 2000 vintage). I havent done a back to back test of the accuracy to be able to quantify the effect of the strut, but my rifle shoots pretty good.
This picture is ten shots fired a 100yds. Took me about a minute to fire off this string. I was using a TruGlo 1X 30mm red dot sight. My rifle also has the Amega Ranges Scout rail which is supposed to improve accuracy.
I estimate that to be about 3.5in vertically, and 2.5in side to side. Not bad for a bum with glasses and a sight with no magnification.
If it's a new from the factory mini, I really don't think you should need one. Seems like they do make a shorter version of the accustrut for short barrels though. the problem is that the one I need it on, the barrel is actually less than 16" and I get the legal 16 with the permanently attached flash suppressor.