EXEC

I had the same problem. Call Surefire and set it up to return the forend to them to be retrofitted for your Benelli. It's a simple process and they shouldn't charge you anything. As to the different parts serial numbers, no clue. All I can say is that you MUST test your M1S90 with the exact load you want to use so you know whether functioning is 100% [some M1S09s will not fully cycle with LE low-recoil 00 buck or slug ammo.] Good Luck