I had the .22LR Bremmer that did look like an M16 and found that it worked best with ammunitiion that was dry lubricated bulleted and that was also sold as "semi-automatic". It was the early type that used genuine full size M16 magazines with a five shot convertor insert.
A local club had one of the M1 Erma carbines and it wasn't, shall I say, quite as much a "fun gun" as it may have appeared at first impression. My advice? I'd try before you buy and try with the ammunition that you are most likely to be able to obtain.