Very informative responses everyone, thanks! I had not found the uzitalk forum before and it looks to be a good source of information as well.
The mac is most attractive to me as a inexpensive option to own a .22lr smg. I doubt that it will see much use in it's stock 9mm configuration. I do think I will try to find one to rent before purchasing.
Are there any other options I am missing in the 3-4k range that would offer the ability to convert to .22lr? Personally I had always thought a Reising would be my first purchase but even as a reloader I think feeding it would quickly become expensive
Thanks everyone for the advice