In a barrel roll, the aircraft rotates both in its longitudinal and lateral axes, while in case of aileron roll, the rotation is only about the longitudinal axis.
What is the difference between a barrel roll and an aileron roll?
A barrel roll is one thing; they can be performed at a positive load factor through the whole maneuver (assuming sufficient control authority). Loops on the other hand will need much greater loadings in the "fast" portions in order to keep the loop "round" and to allow the maneuver to be completed without stalling.
The barrel roll involves an arcing trajectory, and the G-load must be greater than 1-G during the initial pull-up and final round-out. By the way, the "felt" acceleration as described above, is nothing more or less than the net aerodynamic force generated by the aircraft in whatever axis we are speaking of, or in all three axes if we want to be ...
What G forces does a pilot perceive in a "1 G" barrel roll?
A barrel roll is one thing; they can be performed at constant load factor of 1 G (assuming sufficient control authority). In a properly executed barrel roll, however, I do not think there is any point in the trajectory where the vertical velocity is constant.
The Barrel roll is a combination between a loop and a roll. You complete one loop while completing one roll at the same time. The flight path during a barrel roll has the shape of a horizontal cork screw. Imagine a big barrel, with the airplanes wheels rolling along the inside of the barrel in a cork screw path.