I'm not sure of the relevance of this dryfire concept, if you should never dryfire a bow?
Whomever said you should never dryfire a bow is talking about hunting bows. These are flight bows and it is entirely different. They might shoot a 75 grain 20" arrow, which is the same as shooting no arrow. The difference is that the bow was made for shooting a couple of arrows a long way. If it beats the world record it did its job so the damage done while shooting is of little concern.
It is NOT the same as shooting no arrow, there is inertia, I can't be bothered to work out the physics.
The arrow may 'weigh' 75 grains, eg mass x gravitational acceleration, but the bow is accelerating it at more than 1g so it's effective 'weight' is much greater (It's mass of course remains the same)
Del
Now your just getting petty.
A heavy string or double serving would make that difference.
When a bow is considered dry fired at as low as 7 grains per pound and at risk of breakage, and you are shooting 1 grain per pound, for the bows sake, you might as well shoot no arrow. If I stuck a 1 grain BB on it would have mass and not be dry fired by your definition, but it would not help the bow.
Dragonman, yes I have seen several bows dry fired. Some have broken, but most have not. I have seen the string pop off a couple that were dry fired and split the tips out.