Old post but adding info for solving ammo feed issues
I bought the sig version and had issues with several types of ammo first time out. Put fine grit metal polish (the liquid type) on rails and components and cycled while watching a movie. Rinse and repeat as needed. I had to repeat four times until slide felt like it was running on glass. Almost two hours time overall.
After a thorough cleaning saw a number of spots where finish was polished off. Has functioned flawlessly since. I regularly use standard velocity Federal Eagle (the real cheap 38 gr ones) with absolutely no issues. I have noticed wear on the guide rod which will likely need replacing soon. The shock buff is also starting to deteriorate as well. Mind you this is with around 4-5k down the pipe. Also disabled mag safety on the side of m.s. Housing. Was damn annoying. Highly recommended mod. Just take out slider bar & spring. Easy peasy.
After the initial "fitting" of the components, I have been very happy with this firearm. My daughter can regularly shoot 10-12" rapid fire groups at 25 yards with it, and do 1-2" taking her time. I'm thinking the ZRTS ultimate upgrade kit will tighten these groups up.
If you can get these for $400 or less, it's a good deal IMO. Just be prepared to do a little "fitting"