KE has nothing to do with penetration... apparently

Shot placement with a sharp broadhead is #1 factor IMO
Then MO and you can't have MO without KE. I think you can also add in a higher FOC and a smaller diameter also equals greater penetration with all other factors being fairly equal.
I shoot Black Eagle Rampage and Victory RIP for this very reason...best balance of GPI per spine, FOC, small diameter and good overall whitetail weight arrows...My Rampage weigh in at 409 gr TAW and my RIPs weigh in at 460 gr TAW all with 100 gr slick tricks.

When I was younger and IBOs were only like 305 fps I did shoot some light arrows like <380 gr trying to get that flat trajectory...big mistake
I took a shot at a buck quartering away, at 10 yards at a steep angle, and did not get a pass through and only got half of the arrow to penetrate into the cavity...short version zero blood trail and no recovery. Yes I looked and looked for that deer. I won't make that mistake again. #1 mistake was shot placement I was likely high just under the spine and probably got 1 lung, but also arrow weight I am sure with my current set up my arrow would be buried into the dirt on the other side.

 

An interesting article but I wouldn’t get too wrapped up in it. There is the same argument with rifle bullets, you have the KE crowd which favors velocity over bullet weight and you have the Taylor KO crowd that puts greater emphasis on bullet weight. KE, momentum, Taylor KO are all measuring sticks allowing you to measure two different tools (rifle cartridges, arrow weights and velocities, ets) based on criteria. It’s up to you to use other factors like the intended game and add a little common sense to it. Mementum and Taylor KO may be better gauges of performance based on large dangerous game where it is more difficult to reach the animal vitals, whereas KE may be perfectly acceptable for smaller game where the distance needed to penetrate is much less or the muscle or bone is less robust. The hunter needs to assess which category his intended target is. Interestingly the author uses a single bevel broadhead as an example. To be scientifically pure in his argument maybe he should have mentioned that single broadheads rotate as they penetrate so maybe there should be some equation to take into account any energy expended in the rotation of the broadhead through meat at the expense of straight penetration through meat. Just saying….

 

Sorry but I have consistently found 2 things which seem to show up when friends or people I know or people I watch have issues with recovery on deer. Whether that be long track jobs or never recovered wounded deer.....light fast set ups and at times (to a lesser degree) expandable broadheads.

I don't need a bow shooting blazing fast where I can use the same pin for 10-40 give or take an inch personally. I swear my first bow shot so slow I could watch the fletching spin...but I still killed deer because I learned how my bow shot at every distance and shot for the heart not the lungs...they dip I hit lungs...they don't I hit heart.

Now I will admit I think especially hunting out west where far shots are more apt to occur I probably would lighten up my arrows some, but I'm still thinking I need to go heavier as I want to plow through a deer and I know whether my arrow is 400grains or 700grains I am going to practice and know exactly how it shoots at the distances I will shoot....which has changed with each bow...but has never went over 45 yards (still never shot a deer over 27 yards though).



***Just disclaimer this is after eliminating poor accuracy. Accuracy is the #1 thing which I think we all agree. A light field tipped arrow will kill a deer if accurate.

 

As Justin mentioned there needs to be a happy medium.
A train will have a huge amount of momentum because weight is the key factor in that formula.
A human hair traveling at mach speed will have a huge amount of kinetic energy.

Obviously neither are good for hunting, but the example shows the extreme cases.

Some people say momentum is the key factor to penetration, others say it's kinetic energy.

As well, keep in mind this is all based on figures coming right out of the bow. They never say "KE at XX yards".

In reality, if you don't have enough kinetic energy to get the arrow to your target at an acceptable time, you won't have a clean kill / kill at all. If you don't have enough momentum to penetrate when it gets there, again you won't have a clean kill / kill at all.

As for what are the correct values, well basically any hunting arrow on the market will kill an animal as long as the bow is tuned correctly and the arrow complies with the bow specs.

 

Even guys thumping around with longbows and traditional heavy high FOC arrows traveling sub 200fps are blasting through deer for pass-through even though to many fellas shooting compounds probably thinking "HOLY MOSES I can watch that arrow lob it's way to it's target."

Funny thing is I think KE is the speed guys excuse or justification at times. You are correct though you do need both...however ANY bow that has been made in the last 20 years whether out of carbon, wood or an alloy produces enough KE to kill a deer efficiently.

 

This bow made enough KE to kill....

 

Justin, any particular reason for shifting between those two weights? such as going to a heavier arrow because the 380 didn't do what was needed...or...?
thanks

note - Justin has answered this question for us in the bowhunt or die forum.

 

Probably had some bad KE but I'm betting pretty decent momentum with the heavy arrows