I think that the massive attacks (some times of several dozens of people armed with civilian short arms and shotguns) of the Shining Path maoist gang to isolated police posts (1 sergeant, 4 or 5 policemen, usually ill armed only with cal .38 revolvers, S&W Model 10, and 1 MPG smg) maybe the answer to this rather odd ability for a smg. Shining Path terrorists were brutal, with a level of violence unseen in South America. Cheers.