Hi and welcome to the forum. I would not worry about the barrel being damaged by the Blue Sky stamp. I have had several Blue Sky carbines since the late 1980s, and they all shot as well as any other carbine. I am not aware of anyone here on the forum or in my personal experience that has had damage because of the barrel.
Print this target. It is the 25 yard battle sight target. The instructions are on the target. Use this on the bottom 100/150 setting on the rear sight. "Point A" is the center of the bottom of the black area. In your sight picture, set the bottom of the black on the top of the front sight post in you sight picture.
https://www.milsurps.com/images/impo.../L3CkjIW-1.jpg
---------- Post added at 11:26 AM ---------- Previous post was at 11:18 AM ----------
Generally M1 Carbines are 100% reliable with USGI 15 and 30 round magazines, or KCI Korean 15 round magazines. If you have feeding issues, it may be a weak recoil spring. When you disassemble the carbine, measure the recoil spring. It should be between 10 1/8" and 10 1/4" long. If it is shorter, replace it with a USGI one. "Extra Power" after market recoil springs cause more problems than they solve. Also, it is not uncommon for used carbine mags to have spring in backwards. The spring looks like this: /\/\/\/\/\/\/\/\/\ The long side (bottom of the picture) goes to the rear in the magazine.
Happy shooting!