Your photos were interesting.
Perhaps even more interesting is that the bullet base sticking down into the case doesn't make much difference in case capacity. At least not enough to make any substantial difference in muzzle velocity.
According to my calculations, seating a .257's bullet out an extra .27" (as in your photo) results in an increase in powder capacity of 6.8%. This means a potential increase in muzzle velocity, at the same pressure, of 1.7%, or about 50 fps in a typical 120-grain load. This is according to the 1/4 rule, which states that any increase in powder capacity results in 1/4 that much increase in muzzle velocity, at the same pressure. Which is aout as much as we gain or lose between 22" and 24" barrels. It's there, but not much.
Not that adding powder room and barrel length can't gain something. I once owned a Ruger No. 1B in .257 with a throat so long that only 115-120 grain bullets could be seated anywhere near it. In that rifle 3100 fps was possible with a 115, but it also had a 26" barrel. And 3100 with a 115 is pretty much crusing speed for a .25-06.
