Bowhunter Arrow Test
 

Have any of you guys seen the latest issue of Bowhunter? Dave Holt did an extensive arrow test comparing penetration of various broadheads and comparing KE vs momentum as related to penetration. It was an interesting read and the results surprised me a little. My take was that there is not much difference in penetration between cut on contact, chisel point, and pyramid point broadheads, all other factors being equal. KE is more important than momentum as related to pentration. Settle down Arthur, I didn' t do it. :) I wish he had/would have applied some statistics to the results. IMO the results are worthless without them. What is your guys takes, thoughts, opinions?

RE: Bowhunter Arrow Test
 

I haven' t read the article but it sounds like nothing new. They' ve been printing that ' KE is more important than momentum" drivel for a long time. It' s just as big a lie now as it was the first time they told it. If you' ve read Ashby' s study, he goes into great detail on why KE is NOT the prime factor in penetration, BY THE SCIENTIFIC DEFINITION OF THE TERM.

Now, if you take an arrow of given weight, and shoot it from two bows, one shooting it at 220 fps and the other shooting it at 270 fps, you get increases in BOTH KE and momentum. You put up bigger KE numbers with speed than momentum, and since speed sells and lines their wallets, that' s the term the industry insiders want everyone to believe is THE thing.

See, if you take a 350 grain arrow and shoot it at some 300 fps, you get around 70 ft lbs of energy. My longbow shooting a 580 grain arrow at 185 fps only puts out 44 ft lbs. Now if KE was the determining factor, why would my arrow pass thru a 350 pound feral hog, just as easily (if not moreso) as the 350 grain arrow? My arrow carries .4822 lb secs of momentum. The 350 gn arrow carries .4719 lb secs.

Two arrows that will achieve pass thrus. The slow, heavy one carries 37% less KE than the light, fast one. The light one carries only 2% less momentum than heavy one. It' s momentum that is the common factor, not KE. Just looking at that example and using a dash of common sense would have to tell you that Holt' s opinion (and a heckuva lot of other writers as well) of KE being the #1 factor is a bucketfull of hogwash.

But isn' t it a lot more impressive saying your bow is putting out SEVENTY FOOT POUNDS of KE rather than saying your arrow is carrying .4719 pound/seconds of momentum? They' re baffling you with BS because they can' t dazzle you with the truth. :)

Just remember, it' s the little unassuming number with the decimal point that you really want to watch closely, especially when you know your bow is not whacking out gobs of KE.

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RE: Bowhunter Arrow Test
 

Sure I could! Would that make it more impressive? LOL :D

RE: Bowhunter Arrow Test
 

Mez, out of curiousity, what was the target medium Holt was using to measure penetration?

RE: Bowhunter Arrow Test
 

Styrofoam, ethafoam, a green beef hide stretched over raw meat. Arthur, I may be misunderstanding this. In his momentum test the KE was the same for the two different arrows. He had a light arrow and a heavy arrow then shot them throgh a chrony at different speeds until they both had the same KE, which I belive was 50. His conclusion at identical KE the heavier arrow, which would have more momentum, did not outpenetrate the lighter arrow.

RE: Bowhunter Arrow Test
 

Did he do the reverse test and set the two arrows up to shoot the same momentum? If he didn' t, he neither proved nor disproved anything.

How many times did he repeat the experiment? Did he get identical penetration ONCE and call it good or do the experiment 100 times?

How much weight difference was there between the two arrows? Enough to make a significant difference in momentum or was the difference as insignificant as the difference in penetration he found? (I saw one test like this where the difference was a whopping 50 grains. Whoopee.) Was the heavier arrow the same size, brand, model and finish of the lighter arrow? Was it weighted to make it heavier and, if so, how was it weighted to avoid screwing up FOC and spine? Did he use the same size, weight and configuration point on both arrows?

Did he shoot the arrow from identical bows of different draw weights or did he adjust the poundage on the same bow to get equal KE? Was the bow specifically tuned to shoot the heavier arrow or did he just fling it without doing any tuning at all?

Was the foam he used certified as completely uniform in consistency - or did he go down to Hobby Lobby and buy the cheapest old lumpy stuff they had on hand?

That' s always the problem with these magazine tests. They leave too many unanswered questions (that too many people don' t know to ask), don' t account for anywhere near enough variables, and then make grandiose suppositions and conclusions with little or no verifiable and repeatable supporting data. But the undeducated accept it as Holy Gospel and repeat it to all their friends, then those friends repeat it to all THEIR friends, so another myth is created. Or, in this case, reinforced.

RE: Bowhunter Arrow Test
 

Art, reads like one HELL of a start for a letter to the editor... :)

RE: Bowhunter Arrow Test
 

Yeah, but would they print it.;)

RE: Bowhunter Arrow Test
 

There' s only one way to find out :) In this electronic age, a little cut and pasting then email could go a long way pretty easily.

How bout what you said, then throw down the gauntlet and challenge them to re-do the test to your specs...

I' d pay big money for a copy of THAT test :)

RE: Bowhunter Arrow Test
 

Art, all good points, especially about having identical momentum and changing KE, I wondered about that also. To his credit, many of the variables you mention he did take into consideration. He shot each arrow ten times and took an average of the ten. Every shot was through a chronograph at the exact same distance. I believe the same bow was used and each arrow tuned to the bow before testing. For the momentum I believe it was 300gr and 600gr, used aluminum, same length one was 22 something the other 22 also but thicker walled so the arrows would be the same diameter. Gees, I can' t remember all of the gory details. I' ll look tonight and get all the stats, you should buy a copy so you can read it. Still no statistics though, is it signifigant, it is very easy to look at raw numbers and draw conclusions but you can' t draw any real conclusions without proving statistical signifigance. Like you said Art, they publish a bunch of numbers people will take as gospel and truthfully no one knows if they mean anything at all.

RE: Bowhunter Arrow Test
 

Okay, there' s another problem. I don' t know how he got a 300 grain aluminum and a 600 grain aluminum, both 22XX series and both spined correctly for a 50 pound draw. The lightest 22XX series is the 2212 X7. Maybe with a lightweight nibb point and 1" feathers? A 2219 XX75, even a full length 2216, will make 600 grains easy with a 125 gn field point and 5" vanes. But there is a HUGE problem with spine issues, different aluminum alloys and there cannot be any similarity at all in fletching style or point.

Thinking out loud here. If I do cut and paste a letter to the editor, it' s going to be a wooly booger! I' ll hit Wally World after tonight' s football game and see if they' ve got a copy. This is starting to really sound like an interesting farce. :D

RE: Bowhunter Arrow Test
 

Dave Holt performed the same exact test years and years ago and wrote it up in his book (circa 1990), unfortunately the name escapes me at the moment.

I have seen it reprinted in Bowhunter mag a couple of times since.

This may be just another re-print w/ some new pictures. I haven' t seen it this time so I cannot say.

RE: Bowhunter Arrow Test
 

Penetration is no thing to worry about because a 45 pound-plus bow with a sharp broadhead (no matter if it' s fixed or expandible) is gonna pass completely though the chest cavity provided you hit no hard bones. If you happen do hit the shoulder blade or spine, it doen' t matter if your bow is 40 or 80 pounds, your not likely to get a perfect pass through. ...I don' t know, I could be wrong on that. I saw my friend' s 70 pound bow stick an inch in a goats shoulder just like my little bow has. I also saw a 80 lb recurve go right through both shoulder blade and through both lungs somehow. I also saw my little 35 pound bow shatter right through a shoulder and kill a goat. Fluke occurence maybe.

But penetration is not very important. Shot placement and sharp broadheads are what matters most. Not speed, not penetration, or noise.

I think the sharpness of the broadhead is the most important part of penetration. I' ve been lazy before and shot animals with very dull blades. They do not penetrate or kill very well. There are also little things that can hamper penetration, like fishtailing, which can cause your arrow to hit somewhat sideways on the side of an animal.

...Ok, later.

RE: Bowhunter Arrow Test
 

You' re right, Nic. Top to bottom, you' re right. I guess most of us accept it as given that people will make good equipment choices and that they will use sharp broadheads. That leaves this momentum/KE stuff to argue about. And there shouldn' t even be an argument.

Didn' t find a copy of the magazine last night but I did run across my ancient copy of ' Balanced Bowhunting' . Never noticed it before, but Holt was turning into a light arrow advocate even then! Since I still haven' t seen this version of Holt' s article, I' ll reserve further comment on specifics. But in general...

The worst part about this KE/penetration baloney is it' s based on NOTHING but unsubtantiated opinion, backed by poorly designed ' experiments' that are basically geared toward proving a prejudice in favor of light, fast arrows (Holt' s or a goodly smattering of other such ' tests' ). I' d even go so far as to say it' s based a good bit on snobbery.

When you really dig into things though, you can easily see that it' s all smoke and mirrors. Just a cursory glance at Newton' s Three Laws of Motion will tell you a good bit. Kinetic energy isn' t even mentioned. Force, inertia, momentum, acceleration, velocity... These are all there. Where is KE if it' s so all fired important?;)

What really bugs the crap out of me about this kinetic energy fixation is it sets up the anti' s for an attack. If they can take one of those infamous minimum KE charts that are floating around, they can argue, in court, that someone MUST have 40 ft lbs minimum of KE for hunting deer or similar size game. We could not defend against it because they would be using OUR own information! Then they can get a lot of perfectly capable equipment banned. Like stickbows drawing under 50 pounds. Even some folks shooting compounds that draw less than 50 pounds, especially women and children with their shorter draws, would be cut out.

Surely I' m not the only one with enough brain power to see the potential for threat in this!!

RE: Bowhunter Arrow Test
 

How do you calculate momentum? What is considered good?

Thanks

RE: Bowhunter Arrow Test
 

Arrow weight (in grains) X Feet Per Second % 225,200 = momentum

Dr. Ashton' s study showed that the chance of a killing shot when encountering bone increased 80% when momentum was at .57 or above...

Of course, this was for very large african game... how much is the minimum to yield similar results on whitetails is the million dollar question.

Art, Doesn' t Holt' s argument prove that a heavier arrow is more preferable to a lighter arrow, as the heavier one will always have a higher level of KE for a given bow?

RE: Bowhunter Arrow Test
 

Ok Arthur I brought the magazine to work, here goes for the momentum test:
1. 2219 and 2213 cut to same length
2. 5 inch feathers left helical
3. 2219 @ 600 gr 2213 @ 400gr does not specify how this was done, only that
weights were adjusted
4. Velocity calculated to give same KE for both shafts
5. Draw weight changed and bow retuned for both arrows
6. Paper tune each arrow prior to testing at the distance test was conducted, 16
yards, chrony 1 yard in front of test material.
7. ethafoam and styrofoam used because of homogenous nature
8. each arrrow shot 9 times, velocity and penetration recorded
The results are as follows:
Ethafoam
400 gr arrow, 128 gr bullet point, velocity 244.8, KE 53.28,
Penetration 12 1/32 in

600 gr arrow, 128 gr bullet point, velocity 201, KE 53.84,
Penetration 11 15/16

Styrofoam
400 gr arrow penetration 13 3/16

600 gr arrow penetration 13 1/16

His conclusion:
" Data from test 5 and 6 strongly support the theory that kinetic energy, not momentum, is the dominant factor controlling arrow penetration, all other variables being equal. As a reminder, professional engineer Norb Mullaney addressed this same question with a different testing format. His test data support the conclusion that kinetic energy is the primary factor cotrolling penetration when all other variables are equal."

RE: Bowhunter Arrow Test
 

Well, I don' t trust his numbers ' cuz something is plain fishy.

No problem with a 600 grain 2219 with a 128 grain point. That' s simple. Cut it 30" long, 4" vanes and a glue on nock and you' re there. You' d have an FOC a shade under 9%.

Where I think he' s full of meadow muffins is with the 400 grain arrow. The only way he can get a 2213 down to 400 grains with a 128 grain point is by cutting it to 23" and using 2" feathers. Such an arrow would have an FOC of 15%.

The 2219 would be spined for a bow from 45 pounds on the low end to 60 pounds on the high end. A 23" 2213 would spine out somewhere around 100 pounds.

I don' t care how much adjusting you do, the same bow would not shoot both those arrows with anywhere near the same efficiency. Especially considering you' d be shooting the 2213 off a pretty healthy overdraw!

So, even if he did get the weights he claims, and got the speeds adjusted to give equal KE, with an 18% difference in momentum (.4348 vs .5355)... he' s got a 40% difference in FOC! Couldn' t someone just as easily say he proved that 40% HIGHER FOC gives as much penetration benefit as an additional 18% in momentum?

That' s something else he ' proved' without intending to: A heavy arrow at the same KE (at less draw weight) will penetrate as well as a lighter arrow.

He also might have proved that a short, light, incredibly overspined arrow might penetrate every bit as well as long heavy arrow at the prescribed spine.

Or he might have proved that an arrow with 2" feathers will penetrate as well as an arrow with 4" vanes.

Or he might have proved an overdraw arrow will penetrate as well as a full length arrow.

I have great respect for Dave Holt but I don' t buy into everything he says. IMO, he set out to prove a pet theory and so he did what he had to do to ' prove' it. Proven, at least, to those who don' t question the methods. He left too many variables wide open and unanswered.


And then, even if you account for all the variables, one question remains to be answered... Does penetration in styrofoam or ethafoam correlate in any way whatsoever to how arrows will penetrate in actual flesh? I think NOT.

RE: Bowhunter Arrow Test
 

If you are talking Whitetails I think you guys are getting carried away. I simply does not take that much energy to pass threw them. You DO NOT need heavy arrows either. The only advantage to a heavy arrow is a QUIETER BOW and MORE forgiving arrow flight.

I was told that my arrows were too light for Moose (380gr) and I was asking for trouble. Well I arrowed a BIG bull Friday evening and achieved a pass threw right behind his shoulder. It was at point blank range(6 yards) so that definitely helped but I think it would still have done the same at 30-40 yards.

I not even sure what speed my bow shoots at I think around 270 fps so My KE would be right around 60 ft lbs...

RE: Bowhunter Arrow Test
 

Arthur,

Holt could very likely be using nib points and different fletchings (he does prefer feathers though) to get those weights.

And I' ve got to agree with Corey. All this mom. vs. KE is pretty much splitting hairs for North American game save perhapas a Bison, or Musk ox.

I see arthur' s point in limiting equipment by KE levels, and agree that' s a poor way to set regulations.

I think KE/Mom are only rough guidelines. I' ve had my low KE/low Momentum arrows zip through whitetails w/out a hitch, and I' ve had heavier, faster arrows hang up at the fletchs on the other side. Is drag taken into consideration? shaft diameter? blade sharpness?

Way too many variables in equipment, anatomy, and hunting situations to say X or Y is the defacto indicator of penetration value.

IMO, of course.

RE: Bowhunter Arrow Test
 

Jeff, Holt says he used a 128 grain bullet point on both arrows, not nibbs. He might could have saved a couple inches of arrow length by using carbon insert instead of aluminum, but I don' t think we had carbon inserts when he did his little experiment. Too bad he keeps running the same old worn out story when he could very easily update with carbon arrows and keep things more consistent between the 400 and 600 grain arrows. Must be nice to be able to keep drawing a paycheck on the same story, over and over and over again.

Frankly, I put more stock in Ashby' s Natal Study - commissioned by the Republic of South Africa and conducted over several months on actual game animals - than I do on someone shooting two different arrows 9 shots each into a block of foam rubber and comparing the results. When the study says momentum and the backyard experiment says KE...

And I also agree that too much is being made of this momentum vs KE thing, but only to a point. There are two reasons I keep pounding this issue whenever it comes up. First is because of the threat it poses. Second is because putting too much emphasis on KE is doing a disservice to bowhunting. People with light energy bows and too light arrows could very well be causing wounded and unrecovered animals.

The typical hoss shooting a 70 pound supermongo cam that' s putting out 77 foot pounds of energy with a 350 grain arrow... he' s putting more momentum into his arrow than I get with my logs out of my longbow. For people with setups that deliver low KE though, knowing how to maximize momentum while keeping some kind of decent trajectory is critical to give them a clean killing rig.

They' ve also got to realize the low energy they have puts limits on their effective hunting shot distances. Even if they have the skill to hit a ping pong ball every time at 50 yards, their arrows won' t have enough oomph when they get their for a certain clean kill. A reasonable person wouldn' t attempt a shot at that kind of distance, so they don' t need light arrows for super flat trajectory beyond 30 yards or so.

Frankly, I' d really like to see all states institute a 350 grain minimum arrow weight just to force those folks with low energy rigs to shoot enough arrow. 400 grains would be even better, but I' m afraid too many of the mongo bow crowd would get pissed off because of being robbed of a few insignificant fps. Far be it from me to suggest that they should make personal sacrifices for the good of bowhunting.[X(]

Maybe Dr Ashby' s new study with ' modern' equipment will give us a more defined view of the whole issue but, until it' s results are in, I think his Natal study is by far the best resource to look at.