There are one or maybe two manufacturers that make ammo for these on a periodic basis. They are not a .22 caliber short, long or long rifle so don't try to useany of those rounds in that gun. It is closer to being a .22 magnum, but don't try that in it either. Just look around at gun shops till you find the correct ammo. One-Shot in Wenatchee used to have some but I don't know if they still do. With a old in as good a shape as you say that one is, don't take any chances on damaging it.