How much cavity do you get in drywall? The yawing is due to the boattail and the weight of the rear of the bullet compared to the tip. Are your rounds boattail like Russian military rounds?
You don’t know what you’re talking about.
Boat tail projectiles where developed to provide better accuracy at longer ranges. Specifically to take advantage of the transition of bullet from supersonic to subsonic flight.
When I shot CMP High Power match, I loaded Speer 168 gr. Match Kings. They had boat tails. They are engineered for stability.
And working the pit during the match, you might get a little dirt thrown up, but those bullets tend to penetrate deep into the berm.
Furthermore, the bearing surface of a 123 gr. .310 diameter projectile in comparison to the overall length is not long enough to accommodate a boat tail. Such a projectile as you describe would be inherently inaccurate because it would rock from side to side and yaw while it was traveling down the barrel. The rear edge of the projectile would conceivably not be aligned along the axis of the projectile when it exited at the crown of the barrel throwing off accuracy even more, due to gas pressure escaping on one side of the round before the other side.
You’re blowin’ smoke. But I am amused by your stories.