Scope hjght

[greenron15]

I have a Dpms lrt sass I put the Leupold mark 4 3.5x 10 on it. It has regular Knights rings. I know how to find the scope height on most rifles but with the forend this has I can't find the center of the barrel to measure by.
I need this to enter the scope height into Knights Bulletflight program. Can anyone help me
Rongun)