Bow/Arrow Set Up - Kinetic Energy Experiment

[dustyvarmint]

For my upcoming trip to Africa for Plains Game I wanted to see what bow/arrow combination produced the best Kinetic Energy (I'm not convinced momentum over KE is the determining factor in penetration). I wanted to look at facts vs. anecdotes.

After looking at the results I'm not sure adding 100 grains to my current set up, by switching from the Cabela's Stalker Extremes to the XX78's, to gain two ft/lbs KE is worth the time, energy and trouble. The only way I see to make a real difference is to go up to 80 lb limbs.

What are your opinions?

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1) 2009 Bowtech SWAT - 376.8 gr arrow

*Cabela's Stalker Extreme 55/70 cut to 26.5" with 3 Blazer vanes and one 4-inch wrap *26 5/8" measured to AMO standard

*69.75 lbs (maxed out)

*14.6 gr on string (Fletcher TruPeep 8.8 gr, string loop 5.1 gr, tied string nocks .7 gr)

*376.8 gr arrow

*274 fps (three arrow avg)

*62.75 ft/lbs KE (actual, initial)

*Calculated downrange KE and trajectory: 20 yards – 8.9 inches drop, 58.1 ft/lbs KE

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2) 2009 Bowtech SWAT - 360.1 gr arrow

*Gold Tip XT Hunter 55/75 cut to 25.5" with 3 Blazer vanes and one 4-inch wrap

*26 5/8" measured to AMO standard

*69.75 lbs (maxed out)

*14.6 gr on string (Fletcher TruPeep 8.8 gr, string loop 5.1 gr, tied string nocks .7 gr)

*360.1 gr arrow

*279.3 fps (three arrow avg)

*62.31 ft/lb KE (actual, initial)

*Calculated downrange KE and trajectory: 20 yards – 8.6 inches drop, 57.6 ft/lbs KE

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3) 2009 Bowtech SWAT - 476.8 gr arrow

*Easton XX75 2216 cut to 26.5" with three 4-inch feathers

*26 5/8" measured to AMO standard

*69.75 lbs (maxed out)

*12.3 gr on string (1/4" G5 Meta-Peep 6.5 gr, string loop 5.1 gr, tied string nocks .7gr)

*476.8 gr arrow

*246 fps (three arrow avg)

*64.01 ft/lb KE (actual, initial)

*Calculated downrange KE and trajectory: 20 yards - 10.7" drop, 58.0 ft/lbs KE

thanks, dv

 

[TOM]

I would go with the heaviest arrow possible. Have you thought of weight tubes at all? You are probably more than fine with your setup but heavy is always good.

 

[Gerhard]

Dusty,

I would suggest looking at arrow weight between 420 to 450gr arrows.

What broad heads do you want to hunt with?

I would suggest using a fixed blade and if possible cut on contact like a Razor Trick to maximize your penetration..

 

[dustyvarmint]

Thanks for the replies.

I'm planning to use the 100 grain, four-blade Magnus Stingers. TOM indicated some blood trail problems with them, however, which gives me some concern.

I'd e-mailed Gary at Slick Trick and he recommended the ST standard or magnums which I already have a lot of.

My quandry on BH choice is the resulting KE I'm obtaining from my short DL with a maxed out bow and no real difference in KE between a 376 gr arrow and a 476 gr arrow. I'd use the ST, but I'm worried about using a non-COC BH with my KE.

thanks, dv

 

[enysse]

I really liked the lastest article in Eastman's Bowhunting Journal. They had a big article on momentum and Kinetic Energy and how much a arrow should be forward weighted. It brought up a number of good points.

The one thing I took away from the article is how much better a heavy arrow is in providing penetration.

 

[Killzone]

Is it possible to switch to a 125 grn Bhead without changing the spine too much Dusty ? If possible you gain 25 grn and increase your F.o.c

 

[NUys]

Hi there dustyvarmint,

If I were you I would not get too technical about K/E and poundage on my bow setup. I know there is norms and standards that must be followed to bow hunt, but in my experience a setup within these norms and standards that hits the target all the time will never let you down!

For hunting Plains Game I would not go too heavy on my arrows, rather generate more speed for Impala and Warthog that are known to string jump and get your bow as silent as possible.

Enjoy your hunt!!!

 

[INGOZI]

Dusty,

The biggest factor that will determine your success is your shooting ability, you must be able to place your broadhead tipped arrows with pin point presicion.

Secondly you will most likely be shooting out of a hide or treestand with the max distance being about 30yards. Therefore beef up your arrow weight slightly, around 8grains per pound draw weight and choose a good quality fixed blade broadhead. Also ensure that you broadheads that you hunt with are truly scalpel sharp.

All the best of luck and enjoy your trip!

 

[dustyvarmint]

I would go with the heaviest arrow possible. Have you thought of weight tubes at all? You are probably more than fine with your setup but heavy is always good.

Tom,

Thanks for the weight tube suggestion. I am looking at that seriously.

Thanks, dv

 

[Dox]

Hi Dusty

I would recommend you to use a 450gr - 500 gr.Bow poundage should be more then 60lbs.I recommend No. 3 set up.

Dox

 

[TOM]

Tom,

Thanks for the weight tube suggestion. I am looking at that seriously.

Thanks, dv

Check out Three Rivers Archery supplies. They have them in numerous weights. Don't go crazy though, it can change the spine of your arrow pretty quickly.

 

[Paolo Mauritania]

The considerations between kinetic energy vs. momentum is not anecdotal, is physic. Both use mass and velocity for the calculation, although in different form (kinetic energy uses speed squared, and half of the arrow mass so it gets a little confusing; while momentum uses mass and velocity); one of the problem with velocity is that resistance to penetration of any medium increases with the square of the velocity, that means doubling the velocity, the resistance increases four times, and so on. Mass is the the only variable that does not change, high mass at low speed, compatibly with a decent flight path, has more penetration ability.

The old experiment with a 5 gallon plastic pail filled with sand and fired with both a .357 magnum and a heavy hunting arrow; the bullet will be stopped by the sand, while the arrow will penetrate the pail completely. The .357 magnum handgun has a 158 grain bullet traveling at 1250 fps, for a momentum of 0.83 slug-feet per second, and a kinetic energy of 520 foot-pounds. A 710 grain arrow at 183 fps has only 0.57 slug-feet per second of momentum, and a mere 52 foot-pounds of kinetic energy.

Heavier arrow also increase bow efficiency (proportionally up to ~12-13 GPP), lower noise, and vibration. As usual it is always a trade off, for skittish animal I would go lower mass ~600-650, than for the big boys, string jump is due to noise, so we are back to bow efficiency. There are also other penetration enhancement factors to consider into the whole arrow system.

In defense of the old physic.

 

[archer36]

Not much difference in KE in the three setups. If you are shooting 30 yds or less, go with the heavier setup. If you may be making shots over 40 yds, go with the lightest setup to flatten trajectory.