HANK:
   There are a couple of reasons why someone might do this. One is to get a greater charge of powder in LR shooting.   This was done in early days at Creedmoor, because the .44-77 ctg wanted a little more velocity for optimum performance at 1000 yd.   Obviously, this would allow loading more powder.
   Another reason is the desire to breech-seat (or muzzle-load) the bullet, practices often used by schuetzen shooters as they could get better accuracy as compared to fixed ammo.   
   As to pressures, that will depend on many factors.  I don't think there is any reason for concern in either instance, and probably even no reason to wonder, except maybe idle curiosity.

CHRIS
RGChristensen