It can depend a little on where you mount the scope. The TAO1's have shorter eye relief, so where you should mount it on the rail will depend on where you place your cheek on the the stock. If you have an aggressive nose to charging handle stance, you can pretty easily mount the TAOq so the rear of the lens will be ahead of the BUIS when its folded down. In whcih case all is good. If you have a less aggressive stance you will need to mount the TAO1 all the way beck. In which case you probably will need the cut in the small apperature of the #40.