Sorry, " not good" for deer. Maybe marginal or barely adequate but not good!

243 was designed by its makers for varmits. 243 or 6MM, either one is a right fine varmit rifle cartridge for the longer shots and picks up well where a 223 leaves off. Excellent for that size of " game." Last time I checked deer are substantially larger than most varmits (except maybe in Florida).

Deer hunting? Seriously? Why go merely " marginal" or " adequate" -- what happened to folks striving for " excellent?" I' d recommend it as good cartridge for a kid who hasn' t muscled up yet for something in the 260/270/ 7mmMag,308/30-06 range OR for someone with a damaged shoulder or Rheumatoid Arthritis.

Hunting situations doesn' t always pan out as planned, come the " moment of truth."
Shot placement on the bench don' t always equate to " shot placement" in the field.
It is good to have a " margin" for error OR for the tougher than usual individual animal.

For the game' s sake,

Never Go Undergunned,
EKM