I dunno. It doesn't look very fun, almost like a Chauchat. Manedwolf can have all the STG-57s that were meant for me.
Doesn't look like fun? It's basically a K-31 refined into a semiauto. It even kept the bolt handle in the form of the charging handle! (It's the exact same metal beer-keg-looking piece as the K-31's bolt handle)
VERY smooth action, I got to handle one. Take a sheet of glass, put down oil, and slide another piece of glass over that. That's what the action felt like. Everyone who has fired one that I've talked to said that it's a pleasure to shoot, doesn't punish with recoil, and frighteningly accurate. The reason why it was eventually phased out as a general design was that it was extremely expensive to produce.
The action lives on in the form of the SIG AMT, which is, I believe, still in production. It's a .308 version, tuned for even more accuracy, and given wood furniture. But you can't import those, either.