If you are going to try and return it, do so before you take possession of it (paperwork). Deffinately don't shoot it then try and return it. S&W MP sport is in your budget and is proving to be a fine rifle. No dust cover or foward assist.
If you do take possession of your rguns rifle, go to the range and shoot some xm193 for a number of rounds to check function. Then start introducing different brands of steel and different mags to continue checking compatibility function. It may work it may not. I have no idea if my rifles shoot steel as I never buy it. m193 and m855 only.
Good luck and have fun!