
Originally Posted by
cyclepath
OK, lets talk speed lose in bows. I know that some speed is lost do to how much poundage the bow is set at. How much speed is lost shooting 60#compared to 70#? Does this increase as the poundage drops, say shooting 50# compared to 60#? In other words would you loose more speed between 50 to 60# or between 60 to 70#? What over all speed would you loose shooting 50# compared to 70#? Of course this would be done using the same grain arrow. Do these figures work the same with all bows or more so with speed bows? What say you?
From my few personal bows ranging between 50lbs to more than 80lbs over the last +/-15 years I've found that they typically ranged from 2.0 to 2.5FPS/LB........my current Bengal, between 60 - 68lbs, worked out to 2.47fps/lb.
Each bow and it's efficiency within a weight range, the arrow weight and various set-ups would be different to some extent........just like IBO ratings are different between bows for same draw weight, so would this loss or gain (to a much lesser degree).
This reminded me of a book I have from about 1990 called Balanced Bowhunting by Dave Holt. In it talks of improving trajectory and one of the things mentioned is draw weight, where he states "Arrow speed will increase approximately 1 3/4 FPS for each pound of draw weight that is added".
His example is discussing an old round wheel bow set at 55 lbs, shooting a 620gr arrow at 170fps. Bow efficiencies have improved a bit since then.
2009 Martin Bengal M2 Pro Cam w/factory STS & CCS.....66lbs, 29" DL, 422gr @ 272fps, Winners Choice string/cable, Trophy Taker drop-away Rest, Scott Release
1996 Martin Firecat XRG Pro Series w/Ultra Sonic wheels.....69lbs, 29" DL, 465gr @ 245fps, w/fingers & Martin leather glove