How to figure KE/ Help pick a arrow

[ssoden]

Looking for some help ... working of a arrow for this yrs Elk hunt .. which would you shoot? They all shoot great for me out to 30 yrds.

500gr @ 181 fps
580gr @ 173fps
675gr @ 160fps

[clayton95]

I would go with the heaviest one.  Better penetration on a big animal. Good luck on your hunt!

[ssoden]

That was my fisrt thought as well .. but looking for some help to assure from KE stand point that it would be the correct selection.

[RUTANDSTRUT]

if they all shoot good and the heaviest one has acceptable trajectory for ya, thats the one i would use.  there is not much seen difference in trajectory between 20 fps especially if shooting traditionally (no sighting system) but there will defintely be a good difference in penetration.  penetration is paramount especially on a big animal.

[awbowman]

K.E. does not equal penetration in trad archery (at least not with the speeds I shoot).  Momentum governs.  

Having said that I don't like higher velocity light arrows OR super slow arcing shots no matter how much arrow weight I have.

I think you should shoot for around an 11 grain per draw weight arrow weight with significant FOC.  I would try to keep my shots within what I call a "point of aim" trajectory which means I do not have to substantially compensate for distance.

[Dean Lintz]

If you want the formula is speed x speed x arrow weight divided by 450240. This will give you your mathmatical kenetic energy.

[Soilarch]

Arrow 1=1.78 N/s
Arrow 2=1.98 N/s
Arrow 3=2.13 N/s

Those are momentum figures

Arrow 1=36.4 ft/lbs
Arrow 2=38.5 ft/lbs
Arrow 3=38.4 ft/lbs

Those are KE figures.

I put more emphasis on momentum them KE...but that's a big can of worms that will never be put to rest.

I'd pick the 3rd arrow (675) since it's almost an extra 10% momentum for a trade-off of less than 1% loss in KE...but that's me.

Pick which between arrow two and arrow three based on which ever one your most comfortable shooting/making

[ssoden]

Great info guys .. Thanks for the help!!!

[AKCrazyhorse]

One of the "bright line" numbers throughout the Ashby reports is the total arrow mass at which point the heavy bone breaking threshold is reached and maximized.  That number is 650 grains.  The outcome is so convincing that via PM Doc Ashby told me that regardless of FOC changes (extreme to ultra-extreme) he'll never hunt with an arrow less than 650 grains on large animals ever again.  That was good enough for me.

[Night Wing]

The speed is mentioned and the overall weight of the arrow is mentioned, but what isn't mentioned is the bow's poundage. I'm curious. What poundage are you shooting for all of these arrows and speed for each?

[ssoden]

Not sure what I bow has to do with it .. the numbers are what they are no matter what bow I'm using ... but to answer your question I'm shooting a Centaur bow 53.5#

[Zbone]

What is kenetic energy?...(that was a joke folks...8^))

Okay, okay but you guys do have me curious about the momentum formula?

[ssoden]

It's the thump you hear when the arrow hits your target  

[Night Wing]

Shooting 53.5#, if it was me, I'd go with the #2 arrow weighing 580 grains simply for the trajectory with a moderately heavy arrow.

[awbowman]

I think Night Wing is right.  I'd stick to something in the 575-600 grain arrow and get a little flatter shooter.  You have plenty in that bow and who knows, a 30 -35 yard shot may present itself.

[ssoden]

Night wing/awbowman .. I see your point and agree with your suggestion. Thanks

[Rob DiStefano]

Originally posted by ssoden:
Looking for some help ... working of a arrow for this yrs Elk hunt .. which would you shoot? They all shoot great for me out to 30 yrds.

500gr @ 181 fps
580gr @ 173fps
675gr @ 160fps

if "they all shoot great for me out to 30 yds", what's the problem?

i dunno why people lose site of what's most important about hunting arrows - 9 to 10gpp weight or more, fly extremely well from their chosen bow, have truly sharp coc broadheads.  the rest is meat in the freezer.

[ssoden]

Rob ... I have no problem with arrow weight, have always used a 600+ arrow with all my hunting. I just wanted to try and understand a little more than "it's heavy" to assure the most efficient arrow. All the arrows listed are is the 9+ gpp range that I've asked about .. just which is the most efficient is the question.

Thnaks,
Steve

[Rob DiStefano]

Originally posted by ssoden:
Rob ... I have no problem with arrow weight, have always used a 600+ arrow with all my hunting. I just wanted to try and understand a little more than "it's heavy" to assure the most efficient arrow. All the arrows listed are is the 9+ gpp range that I've asked about .. just which is the most efficient is the question.

Thnaks,
Steve

you already have yer answer - the arrow that flies best FOR YOU at a minimum of 9gpp (but i would prefer at least 10gpp).  technically, heavier is s'posed to offer more penetration.  but a well flying, accurate arrow, with a sharp coc bh will always trump all the other criteria.

[JimB]

I agree that any of those would work.The last few years I have been using heavier arrows than what I had the previous 40 or so and I like what I see so far.My personal choice would be the 675 gr.

If you like to play with figures,I would forget the KE and rely more on momentum.

Here are the momentum figures for your arrows listed:500 gr-.40
       580 gr-.44
       675 gr-.4795
To figure that,fps X grains of weight then divide that result by 225218= momentum,measured in slug feet per second.

Good luck on your hunt.