Were you alternating back and forth. Or did you shoot all of the 54 grains before your started shooting 64 grainers? I ask because I am wondering if you simply developed a gas leak. I am an AR15 guy. But I know that the Mini14 is also gas operated.
Romans 1:16 I am not ashamed of the gospel, because it is the power of God for the salvation of everyone who believes: first for the Jew, then for the Gentile.