Air Density and bullet stability question

[Texas10]

A thought came to me while reading another thread on bullet stability where I realized that some of my best groups occur when I am shooting in rain. I typically shoot a boat tail design bullet in the 50 to 69 grain range out of my 223 and have mixed results between these and flat based bullets.

I have read that a flat based bullet exits the barrel at bit more cleanly, breaking free of the barrel crown in a more crisp fashion where as a boat tail design bullet experiences a transition period of " half in and half out" of the barrel with high velocity gases pushing indiscriminately at the boat tail as it exits. And that this causes a boat tail bullet to wobble a bit more until it gradually is stabilized by centripetal and aerodynamic forces, and this is why boat tail bullets shoot better at distances over 300 yards where as flat based bullets are better below 300 yards.

This, and a comment left by Darkker about air density had me wondering if the additional drag influences caused by rain might be tending towards stabilizing a boat tail bullet faster at 100 yards.

One of my favorite off the shelf rounds is the American Eagle varmint tipped (AE223GTV) cartridge. I can get these for as little as 30 cents a pop ($70.00 for 200 delivered to my door) and like to shoot these as a "bench mark" before and after shooting a hand load cause they are so consistent. Although I can get hand loads to shoot tighter groups at 100 yards, nothing I've loaded so far can shoot as well at 200 or 300 yds as this cheap off the shelf round.

The American Eagle is loaded with a Hornaday V-Max 50 grain look alike, albeit with a charcoal colored polymer tip instead of the trademark red tip, and it measures identically in OAL and base to ogive and IS a boat tail bullet. And using only my ( no longer young ) eye I can see no difference in profile or taper. But I can find no information as to who actually manufactures this ammo and what bullet is used. The Federal website does not list this round.

So my questions are;

With regard to BT vs FB, how much of a factor is air density as regards to size of groups at 100, 200 and 300 yds? Are we talking .1 moa difference or more like .5 moa?

Here in Central Texas we typically have hot and humid summer days, both of which factor to reduce air density. Are flat based bullets the ones to use during summer conditions and boat tail during the denser air typical of winter conditions?

Thanks in advance for your advise and experience on this somewhat complex question.