Ruger will check the barrel for straightness. They have a jig which holds the barrel and receiver assembly. Attached to the jig is a gauge which tells how many thousands of an inch the barrel is tweaked when the barrel/receiver is rotated 360 degrees. The barrel is then tweaked and returned to the jig. It is possible to get it to 0 degrees deviation but this takes a little more time and Ruger generally seeks a 4" group at 100 yards. Mind you, the test range at Ruger is only 25 yards.
Where the barrel is bad, Ruger can replace it. In case you didn't know, Ruger does not manufacture their own barrels for the Mini14. They have only 4 hammer forges besides some rifling machines; and this is not enough to meet overall production demands. So, Mini14 barrels are subcontracted out.
On the matter of the XGI (.308 semi-auto), Ruger's engineers had a problem with the 5th shot which was always a flier. They finally solved it by making the slide heavier; a solution Bill Ruger really didn't like. 20 pre-production prototypes were made and all that was needed was Bill Ruger's final approval. Bill Ruger decided not to go ahead with the XGI for economic purposes. He would have to retool a production line and this would cost him about $1 millon. With the Mini14 in regular production (and making him plenty of profits), he saw no need to produce it as it would take him too long to recover his expenses. So, he cut his losses short and cancelled the project. BTW, the XGI reciever must have been a whopping 10" long (I handled a wax casting of it).