Even the C1s had cuts in the receiver at first on each side of the charger guide. When loading 5 rds from the top your thumb would go down into these. Later it was deleted. Mrclark303, you should be able to scare up a Canadian rear sight, maybe a breech block carrier...there's usually something selling here in Canadaicon if I look, but don't know what the legalities of sending it to you would be. We'd both probably end up in jail...