Arrow weight for elk Kinetic energy

[herb0166]

Great thread!

Although my bowing hunting experience is limited to stand hunting whitetails in MN, I might have some helpful info. I am an engineer and just wanted to weigh in looking at this through the lenses of physics. First, the top two things are going to help are bow efficiency, and arrow efficiency. In other words, bow efficiency is the percentage of the potential energy from your bow that is transferred to the arrow? Arrow efficiency is how much energy is lost due to drag during the arrow flight? With an efficient bow, what I think of is the "feel" during release. How does the bow shot and sound when it shoots? Clean, smooth, and tight, or loose, shaky, and dull? Arrow flight, that comes down to aerodynamics. This can be broken down into drag, and arrow design (straightness, finish, etc.).

There is an online ballistics site for arrows where you can look at drag (I assume): http://www.bestcrossbowsource.com/crossbow-arrow-ballistics-calculator

I held the initial energy constant for two situations: 510 gr vs 325 gr. Results: the heavier arrow held it's energy longer. Why? Less drag on a slower moving arrow. Trade off... slower arrows drop move.

Increasing the draw weight, and/or length will increase your potential (max momentum/energy/velocity), but often those are fixed to the individual.

 

[JLS]

In my limited experience, the shots higher up the body tend to not produce great blood trails. That was my first thought when reading your initial post, and then the picture of the elk you posted shows a shot above mid height. Deadly shot for sure, just one that tends towards poor blood trails.

I agree completely. Move that hole down and forward. Not all double lung shots are created equal, and there is a lot more vasculature in the lower and frontal part of the lungs. I’m not at all surprised that didn’t leave much of a blood trail.

Skinnier arrow shafts will help penetration as well. Another fan of FMJ shafts. Match them to your setup, and go 125 broad heads if you can do so within the limits of your bow and shafts.

Use a cut on contact design for your broad head and make sure it’s super sharp. Nice bull.

 

[TrickyTross]

I built my arrow last year after researching and preparing for our elk hunt last year. From my research, I wanted one arrow. I made the football comparison to how I want my arrow. I want something that hits like Julius Peppers (Defensive End) in his prime or Captain Munderlynn (Strong Safety) who can hit you hard with some speed. So I tried to make Ray Lewis (Linebacker) to try and get the best of both worlds (KE vs. Speed). I am no guru by any stretch of the imagination. So bear with me if youd like.

I have a 27.5" draw so I'm pretty limited compared to the folks who have 29" and above and can send a 550 grain arrow down range in the 270+ range. I knew I wasn't going to be able to do that. During my research, I discovered Front of Center or FOC %. Lots of the trad dudes have it as one of their primary factors when building arrows. So I reached out to a few and then saw a couple folks using it for compound hunting set ups. https://www.realtree.com/brow-tines-and-backstrap/foc-and-bowhunting-arrow-accuracy is where Id go to learn more about FOC.

Anyway, all that considered led me to building a Black Eagle X-Impact 30 1/8" TL, with a 125 grain BH on a 47 grain collar, at 416 grains with a FOC of 15%. It hits hard. I was shooting that out of a 2013 Hoyt Charger, so I think speed wise was nothing to write home about. I have upgraded to a Elite Impulse 31 and these things are like darts out of it. Might be able to throw some more weight on it as well since I feel I have more speed to play with.

Good luck!

 

[805Bowhunter]

I listen a lot to John Dudley's take on this and go as heavy as you can while still shooting in that 270-280fps. Above 280fps and tuning that arrow becomes much more difficult. Arrow weight doesnt matter if you are hitting all over the place because your arrows wont tune. With regard to blood trailing/pass throughs I made a switch last year that I am going to stick with this year...after years of avoiding expandables with elk, I switched to using a Rage Trypan. I shoot a 72lb bow with a 29 inch draw, and shoot an Easton axis with 50gr of brass up front and a 100grain expandable. The amount of blood lost from the hole was unbelievable. My arrow passed completely through the bull and was pinned in the opposing shoulder. Expandables have made tremendous strides in the last few years and after last year, at this point I dont see a reason to go back. The key with the expandables however is to make sure you have the punch to make it worth while. They obviously dont have the penetration that a fixed does.

Just my two cents. Whatever you choose, make sure its tuned and well tested. Nothing replaces putting the elbow grease into your own shooting setup. Everybody is different and arrows respond differently to every setup. Build a bow, tune the arrows.

 

[EOregonian]

I am not huge on KE but rather concentrate on shot placement and cutting diameter. From my experience and what I see from shot placement in your pic and what you have said about not having blood for 40 yards that's not uncommon for a high shoulder-lung shot. I used to hunt with a guy that shot every elk high in the shoulder or lungs and it was the same bloodtrail nothing for 40-several more yards and then not a lot and I am not dr but I think the blood would pool up in low and not get to the entrance or exit. I have seen everything from 2 blade to 6 blades in my time and probably from 230fps to now 320fps- I am really not that I am old but have packed a few elk . The only thing that makes KE better is if you are going to try to break that shoulder and then-I like G5 montecs as I can't think of much sturdier they have worked real well however this year we have the opportunity to use mechanicals not sure if I will in Oregon but I like the option. GREAT BULL THOUGH!!!!