Weight vs Speed = Penetration ?

[JimB]

Hybrid Bowhunter,I pay little attention to KE figures normally and believe momentum is more relevent.During a similar discussion however,I went back and used my actual chronoed speeds etc to calculate KE to see if it actually dropped as arrow weight was increased.

I found exactly as you did.KE increased with increases in arrow weight.With access to a chrony,anyone can figure that out very quickly.I still find the momentum figure seems to be a better predictor of how penetration increases when arrow weight increases.

Rattus 58,the speeds you list with changes in arrow weight are way off.When I chronoed different arrow weights out of 50-55# bows,it took almost 100 grs of arrow weight to change speed 10fps.You are showing 20 fps loss when adding 50 grs of arrow weight.It can't happen.It would be more like 5-6 fps loss in real life.I assume that is why your KE numbers are off.The speeds just aren't real.

The arrow weights I tested were 10-14 GPP.

[stickbowhntr]

this just keeps getting better with info, thanks

[troutguy]

proper shot placement is the key to your success . shoot a 500 plus grain arrow and put it in the pump station. leave all math to mathematicians

[JimB]

Some African countries have KE recommendations for different classes of game.According to those KE charts,our bows are only suitable for jack rabbit sized game.This,despite the fact that traditional hunters go over there every year and blow clean through the largest species of plains game with bows that the KE chats say are inadequate.Now when you run the momentum figures,these bows compare much more favorably,mostly because of the weight arrows we shoot.

If you haven't read it already,this is a very well written article on the subject.
  http://www.africanarcher.com/momentumKENETICS.html

[Ragnarok Forge]

KE is the measure of energy stored in the arrow during flight.   Momentum describes how the energy is released on impact.  KE is entirely irrelevant to penetration.   The laws of physics have not changed.   A 700 grain arrow travelling 213 fps will kill a rhino.   You have plenty of weight and speed.

[Mitch H]

I have done extensive testing on numerous occasions starting roughly 25 years ago……I have tested using both recurves and compound bows.

It is my opinion that when hunting with a modern compound bow for whitetail size animals, just about ANY combination will work fine for an adult.

It is also my opinion that when using marginal setups(short draw and light draw compounds, or just about any recurve/longbow) that higher momentum is a much better choice for penetration on big game animals.

One thing that is NOT my opinion is that as long as the arrows dynamic spine is acceptable for whatever type of bow you are shooting it from, increased arrow weight ALWAYS equals increased momentum, AND increased kinetic energy. That is just a fact.

I have tried to prove the law of physics wrong with literally dozens of bows with widely varying draw weights, shooting dozens of arrow combinations with widely varying total weights. Physics whipped me every time, with no exceptions. LOL