This is definitely one of the builds of all time

Its not single shot but Im going to start a Cetme or HKG3 build. Its .308, shoots 500 meters reliably, cheap and you have the option to print a receiver or you can bend a flat if thats more up your lane. Centerfire Systems has kits starting at $115, print your receiver or get a flat for another $80. Print the bending jig.