My 870 Express Magnum had a 26", ventalated rib and Rem chock sys. Paid 240.00 used in a gun store w/ three chock tubes and a wrench. After market 18" full rifled barrel it put three rounds of Federal Coppor slugs in a one hole clover leaf at 25yds. (an indoor range the store) w/cheep scope. Nearly took off my shoulder. Went to 2 3/4" express sheels. I now use a B-Squire saddle mount and red dot scope.