I've just aquired a H&R Premier 22 rim fire(yes,there is a space between rim & fire).The top line on the barrel reads; HARRINGTON & RICHARDSON ,the bottom line ; WORCESTER MASSACHUSETTE U.S.A. The left side of the barrel reads H&R PREMIER. The right side reads 22 RIM FIRE. the S/N is506XXX(no letter prefix.)Any information on type or variation, year of mfg. Is it safe to shoot sub-sonic loads in it? THANX