Again, the Flanged is at a lower pressure than the belted. CIP's rating (above) seems low if Kynamco is correct in using 2425 fps for the 300 gn load; I'd thought it was 2350 or even 2300. Since you have the components on hand, you could use them and stamp the barrel ".375 DoubleD" or ".375 D&D" and add the fps rating, maybe 300 gn at 2150 fps, still a potent load.