I have been struggling with mine but that hasn't stopped me from loving it. Generally I get semi reliable feeding if I load the mags with 5-6 rounds and that is it. I have the factory mag and a pro mag and both of them have the same issues, mostly stove piping live rounds because either the bolt doesn't travel back far enough, or because the mag tension is too strong and it pops them up too high before feeding so when the bolt travels forward it will drag the round in an upwards angle and totally miss the chamber. That is the problem I have %80 of the time, and perhaps half the battle is to find ammo that really works, me personally I'd like to find some round nose +p or hotter so it has enough power to force the action back and enough bullet length to catch the chamber on the way forward.
Having said that I haven't really broken the gun in yet so we shall see what further use will do for me. Also be prepared to have a very dirty gun on your hands because it gets very dirty from powder residue around the chamber. It Gets everywhere.
In the case of the sling I used an old steel (brass would work too or aluminum) cleaning rod and cut it down to size and used an old SKS sling. Blasphemy maybe to those who want to replicate a US GI Carbine but for me it was close enough.
Your rear sight grub but could walk up the threads when you shoot regularly, I pushed the sight body far to the left and adjusted the peep far to the right to compensate and just used an Allan key to turn the grub screws as far down as it can to act as a stop from sliding out, Seems to work so far.
If your willing to deal with the headaches it is a fun gun. And at that price it is an absolute steel, especially of your an M1 Carbine fanboy like myself. It's very handy and accompanies me on short bush walks all the time. More fun than a .22 in my opinion!
Dan.