Years ago I stopped using any 300 grain projectiles for 44 magnum. I just think it is pushing the envelope. First off I feel 270 is about optimal max weight for overall performance and 240-255 is just fine (not just external ballistics but terminal, recoil, accuracy, etc.) for .429 projectiles in 44 magnum. This is my opinion and I know guys who disagree.
I have several revolvers and lever guns in 44 magnum. I had feeding problems in one of my Marlins. . IFIRC the OAL case length was right at the limit but still at spec. Never could make them work in that gun. Wanted a hog gun so I bought a stainless Marlin 1894 20" and added the XS sight rail and ghost ring set up and added a forward mount scout scope. So after spending time and money I could not make it work with any 300 grain loads (roll your own or factory). For factory I tried Hornaday, Federal and some Buffalo Bore. My blued Marlin with thousands of rounds threw it ran them but if you short stroked at all it was finicky. After that I gave up not wanting to carry one load for revolvers and one for rifle.