From Dr Ashby's article
"Given two arrows of equal momentum, but with one deriving a greater portion of its momentum from mass than the other, the heavier arrow will change velocity (decelerate) at a slower rate as it passes through the tissues. In other words, the heavier arrow will retain a higher percentage of its impact velocity at any given time period during its passage through the animal’s tissues, thus it also retains a higher momentum at any given point during the time required for the arrow to penetrate."

So two arrows with the same KE but arriving at that KE from different ways, one with more mass and one with more speed will likely not penetrate the same distance. I think my definition of KE was not right.

If you can shoot a bottle cap at 60 yards with a 40lb bow then you can hit a deer right below the chin at that far. Which means no air, blood, or spine. DRT. But I don't recommend it. What bcranch said is good advice. I don't see a reason to do it, it's kinda like using a 338 Lapua for deer.

If you look at the math behind KE you see it equals mass x velocity (squared).... speed is the biggest factor, thus why its squared...also why PO Ackely was able to make a 22-250 out penetrate 30 cals.

Penatration has to do more with how the arrow and broad loose its momentum. Things like shaft size, cutting surface, cutting diameter, sharpness..etc. how it drags through the median it being shot through

Every bow has a sweet spot were the gain in KE is insignificant as you add weight which decreases speed

Outdoorsman, for a simple explanation I have heard it told this way, ke measures how hard something hits, momentum measures the energy,or mass ( idk) required to stop something. Is that in the ballpark?

BOBO,
In regards to your comment about shaft size, cutting surface, cutting diameter, sharpness..etc you are correct. those things play a vital roll. more can be found on that in Dr Ashby's article "Terminal arrow performance: Penetration enhancing factors"
However in the statement about KE and 22-250 VS 30 cal compared to an archery set up you are comparing kumquats to Guavas. the only similarity these have is they are fruit. With your comparison to rifles VS Archery the only similarity is KE. In reality this is not even logical to try to compare. The reason is you have to look at the manner in which these two different weapons kill.

Kinetic energy is vitally important for understanding how high velocity projectiles, such as bullets, act when striking a living target. In these instances, the high forward velocity and high rotational speed of the bullet do impart tremendous energy to living, moisture-laden tissue. As a bullet impacts, it has what we will call an "impulse effect". It imparts some of that high forward velocity to the tissues it contacts, immediately accelerating those tissues to the same speed as the projectile. These high speed tissues than move along the paths of least resistance, creating tremendous temporary wound channels and dramatic shock effect to the animal that was struck by the bullet. Likewise, the rotational speed of the bullet also literally "throws" tissues away from the bullet, just like the spin cycle in a washer "throws" water from the wet clothes in the tub. All this together falls into the general explanation for hydrostatic shock and cavitation.

Arrows kill by hemorrhaging and not by delivering a tremendous shock to the quarry. In order to cause that hemorrhaging, our broadheads must penetrate the animal's vital area, cutting through organs and severing arteries, veins and capillaries to cause both internal and external bleeding, That penetration is best determined by understanding the relationship between momentum (inertia) and resistance (friction). Not to mention breaking through bones when they are struck.
Momentum is a vital when bones or large bones are contacted.
I dont know the last time my self ,or anybody I know, shot an animal and did not hit a bone. Be it rib bone, scapula, or leg bone.

With what you stated a 22-250 will work on Cape Buffalo cause it penetrates deeper than a 30 cal? I would have to say no. Yes Ackely was able to achieve some better penetration with a 22-250 than a 30 cal. However, we are talking about bullets flying at 1000s of FPS and from what I know this was in a test medium, not in flesh where bone was contacted.
Until we have a bow that can shoot our arrows well over a thousand FPS and kill due to cavitation and hydrostatic shock and not hemorrhaging, KE will not give a true depiction of penetration capability.

In regards to your statement about a bow having a max weight that it can be effective at shooting, I am sure you are correct if you are ONLY basing everything on KE and nothing else. But as proven by traditional archers, studies, and science; momentum matters more in archery that KE. So that argument/statement does not hold water. In all my tests I have not found an arrow that is so heavy it decreased its lethality. With that being said, I now have a new project.

I love how people think its so outrageous to shoot only 10 pounds more than the normal hunter.


Sit on a bench with feet held in the air, if you can pull back 80 pounds without wiggling around its an acceptable weight for you.

Not outrageous....just out of your mind... no reason for it.... unless you just want to feel cool

Not outrageous....just out of your mind... no reason for it.... unless you just want to feel cool

Very liberal way of thinking for a hunting site.

Just like there is no reason for a magazine capable of holding more than 10 rounds...

I bet most people here couldn't pull 50 lbs sitting a bench with their feet in the air....who shoots like that?

Nav,

I shoot 72 and I'll be the first to admit, it makes me feel pretty cool

Very liberal way of thinking for a hunting site.

Just like there is no reason for a magazine capable of holding more than 10 rounds...