I bought a used KKM 6" barrel for my G20 and tried it at the range yesterday. It fired perfect all day with the stock barrel but the first mag with the KKM had 3 FTFeeds and the 2nd mag had 2. I haven't added any aftermarket parts to the pistol other than the barrel. I was shooting Georgia Arms 180gr. FMJ. Should I try different ammunition or is there a different problem with the barrel or pistol? Thanks!