There will be additional energy, just not sure how much. probably enough to be academic.What are the pros for a long slide 9mm?
I know for a 10mm it definitely helps in velocity and energy.
I don't think a 9mm would gain a whole lot extra velocity or energy.
Here to learn.
Is it for competition?
I only know that the benefit stops in the neighborhood of 16 inches and friction starts to reduce it beyond that point.