I saw a thread similar to this one on the X7OG while looking for info about the Tippmann Pistol a couple weeks ago, and I came up with something that makes sense in my brain. Trouble is that I'm having HUGE issues trying to explain it, so I'll to break it down:

Basically, since all paintball guns must be set to a maximum FPS of 300, in theory all A-5's will require the same amount of air to launch a paintball at that speed. They will also require the same amount of air to recock the hammer since, again, in theory they're all the same.

Now everyone knows that when you polish the internals of the A-5 it reduces the friction on the hammer, thus making it travel faster and hit the valve with more force. The same also works in reverse as the hammer will take less energy to recock it as there is less friction to overcome.

Since (in theory) all A-5's use the same amount of air to launch a paintball, when you dial down the amount of air coming out of the power tube to the paintball you're allowing more air to push the hammer back, thus reducing the amount of time it's in contact with the valve. Since the hammer isn't in contact with the valve for as long, less air is being let out, therefor increasing air efficiency.

EDIT: Hmm, after reading that I might have confused people, so I'm gonna see if I can explain it another way:

Let's say it takes X amount of air to launch a paintball, and Y amount of air to recock the gun. Polishing the internals reduces Y as there is less friction to overcome, so less force is needed to recock the gun.

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