i had a westerfield 550 abd and bought a mossburg 500 security 18.5" barrell for it,fit right on,now i have a new haven 600ct 20 gauge ,smallest lightest pump i ever felt,i just hope short 20 gauge mossburg 500 barrells fit her.i think they will. my 550 abd had the scalloped bolt and the prettiest stripped wood i ever seen,looked like a factory police gun,i was offered a outragous amount of cash for it,and i sold it.wish i kept it.