Ended up buying the 423m and ground the back off. It does hit that edge on the reciever. I don't know if the 93a would fit this better. Haven't got a clear cut answer. Hopefully they get it figured out..
Is it the 423m or 93a? Cabela's locally doesn't carry either one. Neither did the local gun shop by me who sells Benelli's. I just want to make sure I am ordering the right base(top mount).