Bd, WOW! Once it became apparent that the rain was not going to stop, I bucked up and headed outside when it slowed to a drizzle. I had been shooting arrows that weighed 482 grains so I was anxious to see what would happen with lighter tackle. I took my 482 gn, 408 grain and some 342 grain arrows with me and shot several loops from heavy to lightest and WOW! The lightest arrows were like lazer beams, I really wish I had a chrono because they almost lit the target on fire!
Strangely though, I noticed that the lightest arrows were not really louder than the heavy ones and even more surprising was the fact that the heaviest were hitting pretty much the same as the lightest ones at 13 yards. Now 13 yards isn't much but a 140 gn weight swing is and it would seem that they should've dropped some at least. The 482's were sticking 3" out the back of the bale where the 342's were only half through. Momentum wins over speed again. As soon as it clears up I will retry this again at the public range up to 60 yards.
Is this similar to your findings? The bow didn't seem to care a whole lot about arrow weight as far as the flight path was concerned...