In 1983 I bought a 9mm MAC-10 by RPB/S.W.Danials. The gun and can were $800, The tax stamps were $400 and the sheriff's department had a scam for a "State Fire Marshel Dangerous Ordinance permit" at $50 each item)
I hadn't shot it in 15 years and sold it about 12 years ago.
Accuracy wasn't too bad. Using sub-sonic loads, I could squeeze 4 to 5 shot bursts. At 50 yards, kneading and wire stock extended, the suppressed bursts were about 2.5 to 3 inches. Firing at a half size man steel silhouette, all shots/groups easily hit the target.
I had one box of tracer 115 gr ammo. When I fired at 50-yard paper targets, I noticed the tracers hit the ground at 200-250 yards and ricocheted another 300+ yards. Be sure of your backstop!
Ivan
ETA: When I started loading on my Dillon 450, The first 2 batches of ammo were 9mm, 5000 rounds each. After a couple years of 10000 rounds my friends and I got bored with it. Then it just sat in the vault! I still have several mags to sell but not a lot of interest!