It eases the transition from leed/throat to rifling. This is usually the point of peak pressure and where the bullet gets aligned/re-aligned or not. I believe the current thinking is 1.5 degrees but let PacNor advise you on this. No rhyme or reason to it but an 11 degree muzzle crown is the current favorite, 30 degree case shoulder, and 1.5 taper to the rifling. I'm not smart enough to tell you why.
That's what I figured......I did the recessed crown on my 280AI pacnor did for me a few years ago so that's what I was planning to do again.
