Must be the tip of the projectile? I have one carbine that will not feed anything but military ball, or commercial FMJ that has the military ball profile and I refuse to monkey with the feed-ramp to make it feed a different profile. I do reload and shoot a soft-point 30-caliber Mauser bullet that feeds well, but it has a lead soft point on the nose and not a cavity or a flat-point.
I have a JRA carbine as well as an IBM. I have had no problems with Critical Defense in either. Fulton Armory also recommends it to their customers. As prior posts indicate, most problems are magazine related, so you just have to go thru trial and error testing ( $ ouch).