If the barrel is fully rifled, it's for a lightweight. The standard weight barrels ceased production in 1977 and a fully rifled barrel was never made by remington for the standard weight 20 gauge, they only had the smooth bore slug barrels. This applies to 1100's as well as 870's. Whenever there is any doubt as to wether it's a lightweight or standard weight 20 gauge barrel, if a quarter will pass through the barrel lug for the magazine tube, it's a standard weight barrel, if a quarter won't go thru, it's a lightweight barrel.
