A 40 or 50gr bullet from a .223 works well on cats. Just like a coyote, if you can shoot one directly in the chest as they’re looking at you, they’ll usually drop in their tracks with only a .224” dia hole in them. IMO bobcats are a bit tougher than most people give them credit for. I’ve shot and seen shot a lot of bobcats, mostly at night. A lot of times cats will come pretty direct towards the sound, so at night (or blowing a hand call) they offer a lot of pretty straight on shots. I’ve seen a lot of cats that were hit in the shoulder or ribs broadside. If you’re shooting a .270 it doesn’t matter because it probably got cut in two and is raining fur, but a lot of times when shooting a cartridge suitable for bobcats those hits result in the cat jumping 4ft in the air and hits the ground running. They usually pile up a short distance later but at night they’re sometimes tough to find. To answer the op question, .223 works well but try for a straight on shot.