Meh - i don't know anyone who has tried one on a deer. I will say I'm getting the feeling I can produce better results at long range using a heavier bullet with better ballistic coefficient than the 10mm/200. They seem noticeably more influenced by wind. I have high hopes for the .430 300's should they ever arrive for testing. I have only shot the 200's with 90 and 100 grains of Pyrodex. Sabotloader has pushed the envelope with them so he will hopefully comment.