I have both, and am trying to decide what would be best to use before I start loading up hunting rounds.
My 300blk is a 9" AAC with an AAC Suppressor. It’s very quiet and shorter than my 20" 5.56mm AR. It is heavier, however. Deep down, I want to use my 20" 5.56 but if 300BLK is a better round I certainly won’t mind and the suppressor would be an added bonus.
I guess my questions can be posed as follows:
Is 300blk out of a 9" barrel more or less deadly for a deer than 5.56mm out of a 20" barrel?
Is 300blk a significant disadvantage at shots longer than 150 yards due to accelerated drop and loss of velocity?
The only thing drawing me to 300BLK was the suppressor, really. I wasn’t going to choose it unless it had significantly more power than 5.56mm which it appears not to have.
I’ve taken a fair number of deer with a 9" AAC SBR, suppressed 300Blk. Always use supersonic. I prefer Barnes 110r Tac-Tx. Reasonable placement of your shot will be a quick and capable dispatch. The key is placement. Do not use subsonic which has ballistics similar to a .45acp. I have also taken many deer with 5.56. Almost the same answer…use the right ammo and selective placement and it works fine. Big fan of 5.56 70grain TSX bullet design. A real winner. Both will work if you do your part.
I prefer the 300Blk based on my fairly extensive real world experience specifically with whitetail (terminal effects).
I’d chose the .300 over the 5.56 if I had both in SBR form, but with a 20" rifle you’re golden. You guys are lucky to live in a state that allows deer hunting with .223/5.56.