So, here’s a twist on the question that makes me wonder, offered more as food for thought than a rebuttal of any of the above analysis - I agree that the rotation effectively increases speed of airflow which should increase drag.

The thought was whether the spin also increased a boundary layer of air over the bullet to decrease drag. In this regard, I’m thinking of comparing two round objects to ignore the impact tumbling would have. Say, like a golf ball or a baseball. A knuckleball is slower than a fastball, for example, though I appreciate that’s largely due to the throwing mechanics of each - you can’t throw a knuckleball as hard as a fastball just due to the motion. Similarly, a spinning, dimpled golf ball travels farther than a non-spinning, non-dimpled ball - I understand the dimples create the boundary layer and help to give it lift by creating higher pressure on the underside of the ball (which has air traveling past it faster than the top part, due to the reverse spin).

Bringing back to the original question, comparing two smooth bullets it does seem that neither of these factors would be at play (and of course, the smoother the bullets the less of an impact spin would have on drag), but interesting to think about.