Success! I bought a Lee .309 bullet sizing die and ran 100 Magtech 71 grain FMJ's through it. I used a small amount of Lee case sizing lubricant on my fingertips and lubed the cases just by picking them up to run through the die - very smooth and easy. The bullets started out at 0.312 and ended up just over 0.309.

Initially, I loaded a few cases (Prvi Partizan) by the usual method of flaring the case mouth to accept the bullet and then applying a light roll crimp as part of the seating step (this round headspaces on the rim, not the case mouth). These rounds still would not chamber in my guns, although they didn't have the pronounced bulge that the .312 bullets caused. The problem was the simultaneous roll crimp and seating actually caused them to be about .002 oversize at the mouth. I then loaded some without flaring the cases and without a crimp - this requires that you hold the bullet over the case as it enters the seating die. These actually look like factory rounds and measure 0.334 at the mouth, just .001 over some factory rounds that I have. They cycle and function perfectly through my guns, so I'm very pleased. I have about 700 of these thicker European cases, so I didn't want to throw them away.

Thanks for all your suggestions - I love solving reloading problems! By the way, I would guess the old Ortgies pistol that was mentioned has a generously dimensioned chamber, so it would accept the bulged rounds - an extra few thousandths is all it would take. Back to the bench to load up a few hundred of these.