how much kinetic energy?

[timberhunter]

just wondering how much kinetic energy are your hunting bows producing? and what do you figure is suitable for deer/elk? its been awhile since i have hunted with a bow, so im not up on all the new equipment. i just bought a new hoyt rampage xt and im looking for a hunting arrow and broad head.

[RadSav]

Imagine if you could eliminate all friction from an arrow.  You could shoot a bow with a 5 fps arrow and completely penetrate an old growth fir tree. 

Now picture the feeble little 29 grain bullet of the .22 short rimfire.  It produces over 70 ft pounds of kinetic energy.  Roughly the same as a 70# compound bow shooting an IBO rated arrow at 305 fps.



It is important to understand the limits of your KE, but it doesn't really mean much in the big picture of bowhunting North American big game.  The topic was basically created so manufacturers and shooters could say, "My D*%k is bigger than yours."  So don't concern yourself too much with it as a measuring stick of whether you should or should not hunt deer, elk or bear with your bow of choice.

A good rule of thumb is to limit your shooting distance to approximately one yard for every pound of draw weight.  If above average speed in your bow extend that a little, and if below average speed (as with a long bow) you might want to limit that a little bit.  But in general that's a better rule to follow than what "X" KE is proper for "X" animal.

My wife shoots a pretty good quality bow for speed.  But that is a relative thing since she also shoots only 50-55# @ 24.5" draw length and a 25.5" 500 spine all carbon arrow at around 225 fps.  Her past bows were about 10-12 fps slower than that.  And she is a critter killing machine!!!  Of the dozens of deer she has killed I can only remember a couple where the arrow remained in the animal.  Even on elk she rarely ever has an arrow that stops before penetrating the opposite chest wall with the broadhead.  Her quickest bull elk kill was a shot taken at 56 yards with a 2013 aluminum arrow traveling at point blank 214 fps.  The bull walked five yards toward us and then the five yards back to where he was standing when the arrow hit and he then planted his face in the dirt. The arrow took both lungs and the top of the heart before bouncing off a rib on the opposite side of the chest.  Any adult male without some disability should expect to see better performance than she does with the light draw weight and short draw length.

Knowing that she has some KE limitations we make some compromises with her shot choices and her broadhead choices.  Most adult male bowhunters would never need to worry about such things, but we do with her.  In knowing that on elk she may not get an entrance and exit hole we choose a three bladed broadhead for her.  This goes against what many believe by not choosing a two blade broadhead for better penetration.  But more reliable kills and better blood trails are the norm with a three blade head over a two so we compromise there.  We also compromise in broadhead size by choosing a 1.125" diameter head that is almost 1.75" long.  A short broadhead would be easier to get to fly if her bow is not set up perfectly, but the longer head aides in penetration yet it is not too long as to reduce low velocity cutting/slicing.  And we make her blades from high carbon steel and grind them to the sharpest edge in the industry on our own strip grinding machine.  These heads cut extremely well at high and low velocities, prolong coagulation as much as possible and they penetrate quite well.

As an adult male I pay far less attention to what I put on the end of my arrow as long as it also has those incredibly sharp blades.  And never once have I measured my KE or even worried about what it might be.  As long as I am legally within the limitations of Washington states equipment requirements I'm good to go.  Now if I had a four bladed, steep blade angled broadhead with large vent holes and a 1.5" cutting diameter I might not choose a lightweight arrow from a 50# bow to shoot it out of.  But with equipment within reason I'm good to go on any animal I might choose to hunt in North America.  That is unless I get the call to go shoot a walrus   Then I might take another look at the limitations of my own KE.

[SCRUBS]

As usual, great post RadSav.

[norsepeak]

I'm a big fan of high Ke, but not crazy about it.  I think you should taylor your system to maximize your Ke and your shooting.  What I mean is I don't think somebody should sacrifice good shooting form in the quest for Ke by shooting too much poundage.  Get a comfortable poundage that you can shoot accurately, then modify your equipment to maximize the Ke you setup is producing.  If there is not penalty, then why not?

[dmr400]

Agree with Radsav....I think momentum is more important than ke. My personal choice for a hunting arrow is a thin, heavier shaft. Currently I am shooting Easton Axis Full Metal Jackets, and am very impressed with them. I also shoot Muzzy 4 bladed heads, because they are very durable, cost is low enough that I don't feel bad about replacing one if it starts to impact differently, and I feel the extra blade gives a wound less likely to seal. I am slightly red green color blind however, so big drops of blood are important to me, my friends shooting the 3 bladed version who find it easier to blood trail with smaller drops are very happy with them.

[sakoshooter]

The arrow weight per lb of draw weight requirement here in WA pretty much takes care of any KE energy questions. With this minimum requirement and some common sense, penetration on any big game animal in WA shouldn't be a problem.

[timberhunter]

thanks for the replies! i shoot 70lbs and 27 in draw and i am comfortable with that, so i will need a complete arrow with broad head that weighs 420 grains or more to be legal in wa correct? i bought a dozen gold tip xt's 5575 and weighed on my reloading scale with 100 grain head only come out to 360 grains. so what do i do? i have heard of weighted inserts but does this affect accuracy at all?

[DoubleJ]

Can you drop your draw weight down to 60lbs?  If you're concerned with kinetic energy, that would still give you 64 ft/lb, a quieter bow, and legal arrows, not to mention an easier time drawing and longer, easier practice sessions

[Button Nubbs]

Can you drop your draw weight down to 60lbs?  If you're concerned with kinetic energy, that would still give you 64 ft/lb, a quieter bow, and legal arrows, not to mention an easier time drawing and longer, easier practice sessions

and 60 is plenty to take down a mature bull elk, which imo is one of the toughest game animals in north america.

[RadSav]

thanks for the replies! i shoot 70lbs and 27 in draw and i am comfortable with that, so i will need a complete arrow with broad head that weighs 420 grains or more to be legal in wa correct? i bought a dozen gold tip xt's 5575 and weighed on my reloading scale with 100 grain head only come out to 360 grains. so what do i do? i have heard of weighted inserts but does this affect accuracy at all?

Yeah this states arrow weight requirement is a little unfair for the adult male with a short draw length.  That's a great setup in most states and Canada!  I have to use a WA arrow and an everywhere else arrow since I shoot 27.5" arrows.  Even at my preferred 65# draw weight I still have to shoot the Camo version of an arrow to meet weight in this state.  Or switch to the wonderful ACC Pro Hunter.  But it is the law of the land and sometimes you have to do what you have to do.  With todays bows your performance is still light years ahead of the stuff we used just 15 years ago.  And we had great success back then too!

[timberhunter]

i never even thought to just drop the draw weight. it seems crazy to have to do that to become legal. i understand the law but why would they want the weight to go up with the draw weight? i would think there would just be a minimum total arrow weight and thats it for all bow hunters.

[RadSav]

i never even thought to just drop the draw weight. it seems crazy to have to do that to become legal. i understand the law but why would they want the weight to go up with the draw weight? i would think there would just be a minimum total arrow weight and thats it for all bow hunters.

Used to be that way. Kids & women took it is the arse as the weight was too high for them.  Only reason I can figure is the traditionalists were afraid we would kill too many does and lose seasons.  We have lost some of those doe hunting opportunities as success ratio's have increased.  But I would venture to say that has more to do with laser rangefinders and not bow speed.  But for the most part I've been trying to figure a reasonable explanation for more than 20 years.  Haven't really found one that fact supports.  Though it does make sense to those who base their traditional archery knowledge on conjecture and supposition.

ToddID has been getting more involved with this.  He might be the one to ask as I expect he has a better understanding of what WDFW's view is than I do.

[colockumelk]

thanks for the replies! i shoot 70lbs and 27 in draw and i am comfortable with that, so i will need a complete arrow with broad head that weighs 420 grains or more to be legal in wa correct? i bought a dozen gold tip xt's 5575 and weighed on my reloading scale with 100 grain head only come out to 360 grains. so what do i do? i have heard of weighted inserts but does this affect accuracy at all?

I also have a 27" DL and shoot my bow at 70#.  I shoot a 340 spined black axis arrow with a 125 grain broadhead.  This puts my arrows at exactly 425grains.  If you don't want to drop your bow weight buy new arrows and use a 125 grain head.  Gold Tips make the Kinetics and a 400spine arrow is 9.5 grains per inch like my axis are.  This would give you a legal weighted arrow. 

[demontang]

The state laws are kind of screwed up. Its hard to meet the min arrow weight if you have a shorter draw. I would look at a heavier gr per in arrow or lower your draw. My arrows I had planned to hunt with came up 15gr short of 420gr so I had to step up to 125gr head which screws my spine up or drop my weight which i dont want to do because my bow shoots better maxed out. I ended up getting 300 spine axis and im at 487grs and roughly at 98 lbs of energy.

[sakoshooter]

It would seem to me that you are slightly underspined with GT 5575's. 7595's I believe are more in line with your 70lb draw. This will also give you more weight.