At close range with a semi auto or lever the .22 mag is still marginal. Foxes, porcupines, raccoons, where this varmint cartridge shines. An adult coyote here in the east can go 40 pounds regularly and serious 'yote hunters here bag a decent amount in the 45 pound range. Other western and southern coyotes typically can run around somewhere around 20 pounds. The .22 mag will do fine on these smaller 'yotes, but if you live in the north the bone structure will very often stop these bullets so your shots will have to be head shots, perhaps a dead on chest shot, or to sneak one into the lungs through the ribs. Then again the last two shot selection could see bad bullet deflection or penetration from hitting bone. The .17hmr is an awful choice any bone will destroy the bullet and result in only a bad wound. I know you said rimfire might be your only choice but a marlin lever gun in .357 will shoot .38 specials very quietly and with a good bullet will drop coyotes at 50+ yards hooter loads will get you out to over 100 yards but not as quiet.