My lovely M39

I took my friend to the range and filled up my old shitty work water bottle with water and laid it down at 100 yards. The first shot I smoked it

I mounted a American scope on my Mosin using a BadAce Tactical mosin nagant rail it mounts into the rear sight and I used a medium relief scope mount but it sits to high up so I can't get a solid position to rest my head. So I'm shooting all over and can't get a group to reliably sight it in, dad says it could be the scope but he's not sure