I built one about 5 years ago. Today i also have an AK and an SKS. That cartridge is great fun. So far i have only shot it out at 500 yards. Tulammo is not quite as bad as everyone says.
I got my C39 and my 516 both documented out to 500 yards with cheal walmart ammo. I used federal 55gr bulk packed for the 516. Its a joy to bust steel with a rifle that likes the cheap stuff.