Before fireforming, the .303 cases held approx 49.2gr of powder.  After fireforming they'll hold 53.8gr of powder.  Both are filled to yield a mild amount of compression when seating the 150gr bullet to the crimp groove. The shoulder of the .303 cases are about .402" in diameter before firing, .421" after.  Certainly not a match load accuracy-wise, but I'm sure the fireformed cases will make me some good loads.  That 4.6gr difference is about the same as that I noted in a 7.5x55 sized in a Lee die, and one sized in a K31 specific die.  There would be few, if any, K31 loads that would need that little bit of extra capacity.  NOTE:  I'VE NOT WORKED UP LOADS WITH THE HIGHER CAPACITY CASES YET, THOUGH I HAVE PREVIOUSLY WORKED UP LOADS IN REGULAR 30-40 CASES.