Re: Subsonic .17HMR
PMP, how far and what pests are you controlling?
For short range, Remington CeeBees or CCI CB Longs offer a 29gr bullet @ 725fps or so, good to 25-30yd in some guns, and pretty quiet from a rifle. Digital Dan on RFC regularly pacifies feral pigs at ranges up to 10-15yd with CB Shorts from a Contender Carbine so chambered(same load, Short case).
For REALLY short range work, Aguila Super Colibris run a 20gr conical @ 500fps, but accuracy can be pretty poor over 10-15yd.
Either of these are quieter than a PCP of the same or lower power,; the Colibris are at least as quiet as a powerful springer.
Farther, any match or standard velocity or subsonic labeled round will be lethal as far as you can hit the head or chest of the beast, and the longer the barrel, the quieter it will be.