I just got one of the STG-44's and had a chance to shoot it this weekend. It's a fun gun. mrs. Cannon has never had a semi-auto .22 before, so to be able to spray rounds was a lot of fun for her. I found mine shoots a bit low - I just fired it at about 20 yards and found mine was very accurate with the sights set to 30 at that distance. Windage (at that range, anyways) was non-existent. My sights are set evenly in the middle.
It is indeed heavy, but I feel like Brad Pitt in Fury when I shoot it lol. Honestly, it was a lot of fun. I use CCI mini-mags in it, and had no jams at all. I did have the occasional feed failure - the round wouldn't elevate into the chamber. This was quickly resolved by simply re-cocking the handle a la Ma Deuce. I read this perhaps happens during the loading process of the magazine and has to do with how the round sits. Could have been operator error during loading - if you pull the thumb slide down far so you can just dump the rounds into the mag this can happen.
Otherwise, I'd honestly use this gun for partridge. I think you could make accurate headshots at that distance. I thought it would be useless, but it was actually quite accurate at grouse distance. I was lucky - I picked mine up used for $400, and we hunt in the Wildcat, so carrying it long distances is not an issue.
Cannon