Which loads for defense, specifically from a 10.5" barrel? I see the 110gr offerings have the highest velocities but the sectional density and subsequent penetration isn't what you might want. The 125gr loads are probably a move in the right direction, especially if you are hitting 2000fps or so from the 10.5" tube. They have an AK-like sectional density so penetration isn't an issue.

Aren't there bullets specifically designed for the 300 AAC nowadays that perform optimally at the velocities achieved with that caliber? If so, which ones? Prefer 125gr choices but open to other suggestions.

I see Lehigh Defense has a 194gr subsonic that, while expensive ($2.50 per round), opens up pretty well for a sub.