USCG had Reising SMGs.
I was present in the early 1960s at a "Barricaded Cop Killer" house who had shot two Deputies, killed one and shot the second's arm off. The house was a block house with what was not known a blocked up kitchen pantry. The subject was armed with a 12 gauge and was firing at everything outside. Several patrol units had the emergency lights shot off.
This was pre-swat days. The house was surrounded by several agencies. It was finally surmised that the subject was in the kitchen. Being young and dumb I went with a second officer to sneak up to the kitchen window to observe (?) the subject. On the way someone handed a Reising SMG to the other officer who had negative idea what the weapon was or how it operated. He handed to me. As we crouched under the kitchen window the window blew outward from the subject's 12 gauge.
I stuck the Reising in the window and ran the full magazine though it, killing every bottle, glass, and pot in the kitchen. By now some agency had bought tear gas and employed it. I had ran to the front of the house (Retreated) as the subject came out of the front door firing. It was never determined which of many bullets fired was the kill shot, but one was a 12 gauge slug though the subject's neck.