I used to shoot an M1 Carbine in service rifle matches. Unfortunately, my carbine was a Universal, so those items wouldn't work for me, as the internals are quite different. I did get better accuracy after I polished all the trigger parts and added a better rear aperture sight. The rifle still needed to run wet, though; it couldn't make it through an entire match without being sprayed down with Remoil or jams ensued. I always wanted to get ahold of an issue weapon and see how much better they are over the Universals.
Any real GI M1 Carbine, will outshoot a Universal, Stock, to Stock.... I have a Universal, that shoots a 6" Group at 100 yds, and that is with Custom Loaded Ammo.... specific to that rifle.... and that is the best it will ever do.... Makes a nice varmint gun, for heavy brush country, but that is about it..... Oh yea, the MRS used it to kill her 350# Black Bear, with a single shot.... No one told her that a .30M1 wasn't big enough for Bear.....
