These are small fallow probably similar in size to a coues deer.I’m thinking 22LR subsonic at 50 yards and under, to the head, is probably gonna kill a deer.
Ive killed a decent number of pigs with subsonic 22lr. Not my first choice but behind the shoulder and following up kills adequately but im not stressed if they were to get away. I have shot a few deer with subsonic 308 and lead projectiles. Expansion was good but I won't do it anymore as its just slow and ineffective not worth the trailboss. In a 223 id just not bother.