To put this in perspective, that is a worse group than I got with an M24/47 Yugoslavian Mauser in 8x57, shooting 1955 Yugoslavian corrosive ammo with iron sights. The trigger had about a 1/2" pull at about 12lb and the bore was so rusted and pitted one couldn't even see rifling and black as coal.
I agree with the others that your sighting system is broken. With a working scope you should be no worse than 2" with about the worst quality ammo on the planet. If the shooter can shoot of course.
Last check, is the barrel possibly loose ? I was sold a 308 semi custom rifle
and while I was checking it out, I found that I could rotate the barrel by hand... The barrel nut was tight, but the wrong recoil lug installed with a small diameter pin and the pin had locked up the nut before it could pinch the recoil lug against the action. The only thing tight was the nut against the pin... Could have hurt someone.