The determining factor is, how easy, or hard was it to push the pellets through, once they were started.
My '49 101 is very accurate but a pipsqueak in the power department. My model 110, made around the same time, is a hammer, 600fps with 6 pumps. The reason for this eludes me.
Another thing that will affect velocity is not having a seal between the rear of the valve, and the valve nut. None of the kits come with one, as the factory never used one. I used a thin 90 duro o-ring. Don't feel that puff of air in the face anymore.