Yup, that was some cheap shooting fun ammo.
I remember getting a couple thousand rounds and had a lot of fun shooting it in carbines. Would have a few failures to fire but great for plinking. Yes it was hot and meant for submachine guns. I know a guy who shot several mags of it through a Sig Sauer P226 handgun. Stupid is as stupid does I guess. It was still shooting fine, but when he cleaned it, there was a crack down the side of the aluminum frame!
Back then, Sig replaced the P226 with a new one.
That was back then and later they pretty much stopped replacing guns even for LEO's.