I'm posting this, at the behest of Harm, who tells me there are a few members here who have MAC-11s, but have not heard of (or are not familiar with) the MAX-11 Upper. I'm computer Illiterate, so here's a good pic of the item, right from the manufacturer's site. Its also a good place to read up on the MAX-11, just in case you're interested in it.http://www.max-11.com/
By the way, the guy who created these and manufacturers them, Richard Lage, is located in Gilbert, AZ. He's super nice and easy to talk to. His phone# is on the site, so call him, go by to chat, and take a look at his really cool invention.
The gist of his creation, is two fold. To reduce the cycle rate from the standard (and almost impossible to control) 1100 rounds/min., and to increase the accuracy. Among other things, the barrel is now 8" long, and the cycle rate is now 600 rounds/min. But you do have options on the cycle rate, if you're interested in something a little faster. You also now have adjustable sights and a rail to add on "optics", if that's your thing. For what its worth, Richard also makes uppers for the MAC-10, MAC-10 in 9mm, and the MAC-11s that have had the Sten grip/mag conversion done.
These things are kicking butt in the sub gun match community. They commonly take 1st, 2nd, and 3rd place (or all 3, or some combination there of). They are consistently beating out the likes of the H&K MP-5, UZIs, and AR-15s with the 9mm conversion. I'm not trying to take anything away from these nice (and very high dollar) guns, but just pointing how amazing the improvements are to the lowly MAC-11, that it now holds its own against such impressive competitors.
In a "nut shell", I really love these uppers. Richard has done a bang-up job of taking a low end, non-contender sub gun, and making it into a functional, high performance, reliable tool. And he did it for a reasonable price.
Anyway, as I said before, I'm a non-performer on the computer. So you'll have to ask Harm about my MAC-11. But basically, it's the same as the one on the home page of the MAX site, except with a suppressor, a C-More sight, and although it doesn't change the looks too much at all, mine has had the Sten conversion done...
Good day, and happy shooting.