Opinions/Experience of Elk Arrow Weight

[Bump79]

#2 Some of the Ashby stuff applies, but not all (Broadhead design, materials, sharpness, arrow components and flight, ect..apply.) I don't believe a 650gr (or any specific weight goal) is the standard for me anyway. A traditional bow is not the same as a modern compound. A 70# trad bow and a 70# modern compound will not have the same efficiency. The materials and stored energy launching that arrow are different.

#3 KE and Momentum are only a data point. KE and Momentum are just math equations, and outside of context can be useless. For example, mathematically I can make a 440gr arrow at 280fps (76.62 KE) have the same KE as a 1 gr ping pong ball traveling at 5864fps (76.36 KE), because KE is simply math and you can manipulate the variables to equal whatever KE desired. So KE and momentum can inform arrow discussion, but for me, is not the end of the discussion. If choosing between them, I prefer momentum as a compass...

I'm pretty much in agreement with everything you've said, very well thought out.

I will say though, there seems to be some contradictions between these two points. I agree that a compound and a trad are apples and oranges. You're right and you reference stored energy (PE), which becomes KE once the bow goes off. So clearly KE isn't just a data point as you agree it is the difference between a trad and modern compound. Also, KE isn't just simply math.. it's a key properties of the arrow. The only levers you have to pull to increase KE is changing the archers specs (draw length, draw weight and bow IBO). Which isn't really practical for most who've already worked their way up to a reasonable draw weight. So it's not just playing with numbers - it's physics.

The reason I like KE as a indicator (not as the only factor) is because it is relatively constant with a setup. Once you've got a bow, setup at your desired weight and range KE is fairly static. It does increase marginally with arrow weight though. So If someone tells me their specs and bow - I know their KE and that setups ability to do work. A higher KE setup will have a higher ability to generate momentum. If you know someone's desired ranges and target species, then you can make an accurate grain weight recommendation to arrive at a good momentum value.

I went deep down this rabbit hole and have an engineering background (albeit a lowly one). The vast, vast majority of online calculators portray KE completely wrong and give BS speeds. There is no peak in KE with an arrow weight and it always increases with mass (slightly less incrementally). After all this research and testing, I ended up being able to create an accurate speed, KE and M calculator completely based around KE. How KE increases based on IBO, draw length and weight and how it increases based on arrow weight. KE really is the foundation of a setup.

 

[roadrunner]

Opinion: shoot what flies well with your bow setup and shoot a good dependable broadhead. KE is irrelevant.

Experience: 390 gr arrow flying at 290 fps with a sharp fixed 3 blade broadhead will pass through a 6x6 size bull elk at 30 yds. It will pass through a large cow elk at 55 yds.

 

[Beendare]

28-29" DL.

70ish DW.

8 elk with sub 400 gr, 1 elk with 415gr. Zero issues, big mechanicals. I don't recommend it, but if you hit behind the pin(the biggest issue most face and they do things that handicap that) elk are really easy to kill.

Decent broadhead, reasonable arrow weight, bow actually launching an arrow straight- dead elk.

Yep ^ an avg good flying arrow is a killing machine.

I would recommend ignoring the folks trying to make it complicated......

 

[fatlander]

@billygoat is spot on about hitting behind the pin. I’ve yet to lose an animal from hitting exactly where I was (or should have been) aiming. The vast majority of lost animals were bad shots and a few were from trying to force shots I shouldn’t have.

280ish fps with any arrow that’s 400ish+ grains will do just fine on anything in NA. A fixed head is going to hit behind the pin less than a mechanical. There’s no two ways around that.


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[TripleJ]

Sharp broadheads and good arrow flight matter more than arrow weight. I've killed multiple bulls with 390 grain arrow/broadhead combos at around 285fps. This setup was good for passthroughs on broadside shots, and stem to stern on a frontal shot. I've since moved to a heavier arrow, 460'ish grains TAW, but you definitely don't need a 600 or 700 grain setup for elk. Elk are pretty easy to kill if you hit them where you are supposed to.