I own a Saiga-12 with a 19 inch barrel. The most I have ever hit in 5 stand is 8 out of 25. I am a beginner. The Saiga does not come with a choke but there are aftermarket chokes available.
In this video, some guys are using modified Saigas for competition.
http://www.randrtargets.com/. They are shooting ground targets mixed with flying targets.
I have a stock model and do not plan on modifying it.