Polygonal Barrel Recognition
How can i tell by looking?
Ah... Grasshopper! That comes with experience. However, the best explantion might be does the rifling look for want of a better
term "swirly". Cut rifling has definte defined grooves in the metal of the barrel. While I hate to make broad generalized statements,
look at almost any barrel on another weapon you own. In all likelyhood it will not be a polygonal one.
Once you have something to compare it to it should be easier for you to determine if your USC/UMP has a polygonal rifling.
This is a pretty good pic of cut rifling. If your USC/UMP rifling looks like this, then it is not an HK German manufactured USC/UMP
barrel. The USC/UMP barrels are not fluted while the barrel pic below does have flutes, so you may ignore them and just concentrate
on the rifling.
Hope this helps.