7mm mouser questions

[OldSHO]

I am going deer hunting this year, and will be using a wwII 7mm mouser sniper rifle. but can't figure out how to sight it. it does not have a scope. we took it to the lee kay range yesterday so that I could try to get a feel for the gun. since I have never fired it before. we had four people shoot the rifle all aiming for the center of the target. But the gun shot either high and some times low. but really far to the right. at 100 yards. and with any other gun we hit what we aimed at. we also had a 270 and a 30.06. hit every thing with them. but I was wondering if any one knows any thing about this type of rifle. my uncle has taken it deer hunting and dropped deer with it. but it has been to many years since he ahas fired it to remember any thing about it. any help would be greatly appreciated.