I'm not sure what an M4 scope is and a #5 mount but if this were my rifle I would add a shim to the saddle of the back mount to bring the rear of the tube up slightly. I use strips of plastic Coke bottles but some folks use strips of friction tape in the saddle and build it up until you have your scope realigned with the bore. I prefer the plastic strips because they don't seem to compress and deform like tape will. Also you can use strips from an aluminum soda can. Once aligned with or parallel to the bore you can now use your scope elevation adjustment to dial in you elevation. Some folks will have their gunsmith realign their mounts by milling one saddle ring or the other till bore alignment is achieved but it's always cheaper to try the shim method first.