I bought this firearm 25 years ago. It was very inexpensive and we had a lot of fun way back then chasing cans with this guy. it was a great plinker. I wish it was full auto. I could afford that!
It is an Intratec TEC 22 Scorpion. It uses Ruger 10/22 mags. The original TEC-22 variant featured a threaded barrel and a 25-round magazine. The barrel's threading is 1/2-20 and allows a barrel extension or other accessories to be attached. A small, knurled nut threads onto the barrel to protect the threading.
At the gun show last weekend I saw one that was fit with a suppressor. So I pulled this guy out of the safe. I have not shot this guy in many years because I could not find a gunsmith to fit the broken firing pin.
--I will take this by my new gun smith for a revisit!