The calculations below are based on measurements performed by Ike using 60# compound bow. It can be clearly seen there are some inconsistencies probably caused by use of 2 different arrow types (spine, fletching, weight balance), the test would also be more revealing if the longer range was used (Olympic archery is 76.5 yards). Also, in the future, I would add the diameter of the grouping as lighter arrows may be deflected more.
Results:
SPEED not surpassingly the lighter arrow are faster.
KINETIC ENERGY (KE) not surpassingly the heavier arrows have bigger knocking power.
However, the above statements tell us NOTHING.
Before I proceed here is a disclaimer about ultimate truth: Any arrow, even a light weight, when well placed will kill a deer by creating massive internal/external bleeding when shooting at short range.
As we know from gun hunting you can kill an animal with .177 cal bullet up to 200 yards, but at 500 yards a massive .30-06 round rules the skies with it's flat trajectory and power on impact. It is also true for arrows, at further distances arrow will be slowed down by air resistance, pushed sideway by wind, or deflected by brunches and tall grass. Lighter arrows also make for a louder, more abused bow. If you are shooting further, you should not only upgrade to heavier arrows, but also to matching, heavier bow and your own strength and skill to match that that. Keep in mind that medieval archers were mastering and commonly used 130# bows and in some war scenarios 180#. Most of the hunters today should be able work up their strength up to 80# or 90# which is commonly available in compound bow category.
Calculations:
- 407 gn x 259 fps = 59.21 ft-lbs = 80.2 Joules
- 355 gn x 278 fps = 60.90 ft-lbs = 82.5 Joules
- 280 gn x 307 fps = 58.58 ft-lbs = 79.4 Joules
- 245 gn x 322 fps = 56.39 ft-lbs = 76.4 Joules
1 lbs = 7000 gn (troy grains)
Gravity Acceleration 32.175
1 gn = 64.79891 milligrams
