I have a custom FN Mauser my father left me, He had the rifle built in the 1960's. Is this a good cal for coyotes and what other varmit can it be used on. also how hard is it to get ammo in 220 swift cal , Factory made. I have 50 to 60 shells he loaded from 20 yrs or better, Rifle is in almost new condition. I have a 4x18 or 24 nikon on it.