I can only attest to what I have read, because I do not have one ... yet. The 454 can be loaded through the gate, but it is tight and tricky. Not something that you would want to have to be in a hurry to do. The 45 lc loads through the gate normally. The best way to load the big brother is to remove the magazine tube and drop the rounds in like you would on some .22 rifles. Story goes that it will hold 9 plus 1 in the chamber. 10 rounds of 454 oughta get the job done, and if it doesn't, you might want to have considered not pulling the trigger in the first place.
Been wondering about some opinions on the 454 out of a rifle. Some want to bad mouth the combo for whatever reason, and argue that it isn't as powerful as the 45-70, but it is a good light gun etc. Why is one of the hottset pistol cartridges, that takes on all creatures on the earth in a revolver such a weakling when you introduce it to a long gun. Velocity goes up, It is easier to control recoil, larger mag, more energy, longer sight radius, etc etc. I guess that some of the bullets especially the lighter ones might blow up at the higher velocity, but load accordingly, and use a premium bullet.
Don't want to argue the 45-70 against the 454, because the 45-70 is a compare all cartridge in the big bore world. I am just using it as a reference point.