Interesting, but limited test last night. Same bow (recurve #60) one arrow 9 gpp, one arrow 12 gpp. Shot into a bag target, the 9gpp arrow consistently out penetrated the 12gpp arrow. Shot into different places on the bag, didn't seem to matter the 9gpp always penetrated more. Both arrorws were carbons. I know this is not a definitive test, but interesting none the less, and point to the long time balance point of 9-10 gpp as the place to be.

can you make a 6gpp arrow and try that? the military has long ago figured out that velocity = penetration. Not kinetic energy, not momentum, but simple velocity (obv projectile must hold together). The question is whether this is also true with arrows and broadheads.

Shooting into a bag might not make for a good comparison.

"can you make a 6gpp arrow and try that? the military has long ago figured out that velocity = penetration. Not kinetic energy, not momentum, but simple velocity (obv projectile must hold together). The question is whether this is also true with arrows and broadheads."

I can probably get close to 7, i may give that a try tonight. I will say that on the extreme end, my compound with considerably lighter arrows moving considerably faster will penetrate considerably further in a bag target. Idk, what would happen with the recurve and its lower velocities though

"Shooting into a bag might not make for a good comparison."

This is probably true, but i thought it was interesting none the less :-)

mparker, there is a direct relationship between velocity and momentum. momentum=mass x velocity Jawge

Another factor that affects penetration is friction. Even if the Mass X Velocity result is higher (or equal) an increase in shaft diameter will reduce penetration.

The Momentum comparison is 100% accurate only when all factors except mass & velocity are equal.

My experiences with light vs heavy arrows do not agree with your findings.

There are many more factors to consider other than just weight, one as pointed out is friction. An arrow not spinning on its axis will have considerably more (is the spine correct for both arrows), or larger fletching, tension of the nock on the string, were they both drawn to EXACTLY the same length. You do realize that even though the lighter arrow will come off the bow faster it also slows down faster! What distance to the target?

Bob

This penetration thing has always been a “head scratcher” to me. I have seen where a wood arrow with a 125 grain bodkin broadhead penetrated a bucket of sand from a mid 50’s# bow. But have watched a bear run off with an arrow from a 70# bow flopping in the breeze. That arrow was a 175 grain 2 blade shot by a famous modern archer. Both shots were taken at what we refer to as “Trad bowhunting ranges”. Now if you want to try and tell me bear flesh is harder then steel and sand go ahead, I got all summer.

Years ago I met a compounder who had shot a Brown with a #70 bow and a 5 GPP arrow. Said his guide concluded that the bear hardly had a scratch.

Larry sez a bear is easier to kill than a jackrabbit.

Something doesn’t add up.

Friction is interesting. Seems like a big deal, but it doesn’t matter how wide your tires are - once the brakes are locked up or the wheels start to spin or you start hydroplaning, you’re headed for the ditch and there’s not a damn thing you can do about it. You lube up your arrow with a generous amount of blood, and I have trouble imagining that it amounts to anything. Tissue is going to contract away from the cut unless your 2-blade strikes exactly parallel to the grain of a muscle, so wherein lies the rub? AS LONG AS the arrow is flying straight.

People like to talk about ping-pong balls vs. hunks of lead to make their points when this one comes up, but in the grand scheme of things, a 7 grain arrow and a 14-grain arrow probably carry close enough to the same amount of Energy/Momentum/Inertia at 20 yards that it adds up to naught. At least in comparison to the importance of Tune and Accurate Placement.

All I ask for is a reasonably quiet, properly spined arrow that shoots flat enough to keep me from missing high or low at ranges where I trust my ability to hit down the middle.

Bob,

The target was 19 yards away, the arrows looked to be flying true. the lighter arrows are tuned to that bow, and i have bare fletched them with broadheads and they still hit with my field points. The heavies may be a touch stiff, but if my release is clean, they fly true, they just are not as forgiving. Both arrows are carbons and the same OD. And, while i can't guarantee they were drawn to exactly the same length every time, i would guess there was never more than an 1/8 of an inch difference. I don't snap shoot and have a pretty consistent anchor. I didn't shoot once and call it good, i shot numerous times and the results were consistently the same. And yes, i understand basic physics.

Once again, i am not saying this is a definitive test, just that it was interesting and the opposite of what i expected.

Velocity equals penetration, if the same projectile is used. But we are not talking rifle projectiles.

Milk jugs willed with gelatin, bags of saw dust, commercial targets, etc, have been used by guys experimenting.

Velocity equals penetration even with different projectiles. The 5.56 penetrates steel better than 7.62x51 ar close range, and the old Vietnam era 55 gr 5.56 penetrates steel better than the modern 62gr bullets that have a steel penetrator in them. In each case the lighter faster projectile penetrates better at ranges where it has a higher velocity. At longer ranges the lighter projectile slows more so eventually the more aerodynamic bullet (which tend to be heavier) will outpenetrate the lighter bullet. But it appears that velocity is king, not momentum nor kinetic energy. At close ranges the 55gr and 62gr 5.56 bullets have essentially the same KE, and the 62gr bullets have more momentum, yet the faster 55gr lead cored bullets penetrate better than the 62gr bullets.

This went in about 1/16 of an inch

Live animals are not closed cell foam. I'm sure everyone knows that. However, when we tout penetration it's always foam, or a bucket of sand that becomes the medium, and both are many times tougher than any animal in North America. It's at best a fun project to do, but in real life it doesn't mean much...and if not machine shot, too many variables can manipulate the outcome. If you've been a successful hunter, then you will know what works plenty well for you.

a 125 or 160 grain ACE standard on a cedar or fir shaft works on everything I have needed it to

Just kinda not hung up on inches of penetration

either it works or it dosn't ,is all I care about

Ok, I'll play... I get to build and play either lots of arrows, and we, has hunters know, it's not kinetic energy but momentum we need for penetration. But, we also need arrow speed. Once we drop arrow speed, we loose momentum. Most calculators will figure out momentum up close, but not at 20 and 30 yards. This is were we need chronographs to find arrow speed. But, it you're a crawler, you can see arrow trajectory drop off as we go higher in arrow weight. But without a chronograph, we can't figure what our momentum is, heavy verses lite.

Penetration of an arrow is something that will always be argued. And I've yet to see guys shooting through chronographs and using a shooting machine to do arrow tests.

When I spoke of friction, it way meant as the friction that is applied to it in flight, not in the animal. That friction is applied from fletching size, height, length and whether the shaft is spinning on its axis or still overcoming paradox. If the arrow is not spinning on its axis at impact penetration is decreased.

Bob

I shot some arrows into wild hogs, ,some heavy some light,,so I go with that,,for my penetration test,,

Bob, gotcha. The fletching is the same 5" shields on both arrows. All arrows are hitting the target straight. I don't have any slow mo video, but the arrows appear to to flying good by my eye. I can generally see if my arrows are not true. I would assume that the heavier/stiffer arrows are overcoming paradox faster, because they are stiffer, correct? At 20 yards however, if they were off at all, the fletching has them straightened up at impact.

For the Momentum/Penetration comparison to be fair arrow diameter, fletching size & all the other factors except for arrow weight & velocity must be the same. However friction generated as the arrow penetrates the animal will impact momentum much more than air friction while in flight because flesh & bone are much denser than air. All you have to do to prove this is fire an arrow parallel to the ground into thin air & then do it again w/the same arrow into a ham & compare how far each arrow traveled from where you stood. It's a no-brainer.

Brad, which ones work best for you? My 9 gpp arrow has yet to stay in a hog or deer, but even at 9gpp, it is still 540 grains, so not real light.

Also please don't think i am recommending one or the other, i was just relaying something i thought was interesting and against what i expected to happen. I am not trying to convince anyone of anything, just reporting results of a very informal test

So in summary, the results are quite clear. No matter what type of penetration test you conduct, some will find fault with your testing methods, and some will disagree with your findings. And some will agree with your findings/results. And that's just hunky dory because we all get to use the setups that WE want. I enjoy reading these penetration tests and feel like there is always something to learn. But I have to admit, I really enjoy reading the commentary about the tests. The comments are often out right entertaining. I learned a long time ago that when someone starts a discussion or argument with the old, "I don't care what anyone says, ......" , they really don't.

Thanks for the tests and report!

Lefyt, you are correct, sir! haha

Thank you for your test I find them very useful and I do think they mean something

Was asked earlier in this thread about a lighter arrow, and i was able to compare it this afternoon. The lighter arrow was 7.33 gpp. Final results was the 9ggp was best 12 gpp second, and 7.3 was last. the 12 and 7.3 were actually pretty close, the 9 was consistently noticeably better than the other 2. About 1.5" more penetration.

This concludes our unscientific, but fun and interesting test :-)

Old Fred had it figured out long ago.

I've spent a considerable amount of time trying to disprove him, and haven't succeeded in that yet.

9 - 10 gpp gets it done deeper every time.

Rick

Good test, thanks for sharing. The best part is YOU did YOUR test with YOUR equipment to figure out what works best for YOU!

"This is probably true, but i thought it was interesting none the less :-)"

And it is indeed interesting.

Here's another factor to consider and that is the response of the target to the impact. I'm thinking that a heavier arrow will move the bag a bit more which will have an effect on penetration.

Maybe we approach "penetration" tests all wrong. Maybe we should shoot blunts at a pendulum. The arrow that moves the pendulum the furthest wins. :^)

Rick, I knew that you had proven that out more than once, and when i saw the arrows in the bag, i immediately remembered you saying that. I didn't really start out to do a test, was actually just curious how the heavies would shoot off my bow. Just happened to shoot them in the target with my standard 9gpp arrows and thought, that is interesting. Shot them several more times with the same result. Then capped it off with the lighter arrow today.

So, I'll give you something else to think about in turns of penetration... I started shooting single bevel heads several years ago, never had the penetration most here claim. So, last fall, I started thinking.. As a single bevel cuts, it turns. It doesn't go straight through in a line, but will turn to the right or left, depending on the bevel. On broadside shots, maybe it doesn't matter, but on quartering away or to shots, how much of the arrows energy and momentum is lost as the head turns? It's gotta take energy to turn, it doesn't pull itself like several claim it does. So, my question is, how much energy is lost with the head turning?

I've see pics of straw shards sticking into a wood sided house after a tornado. Straw is pretty light. Must have been speed.

I bet you everything I got that my 109 mph arrow out penetrates your 350 mph straw shard.

You gotta bet Joe...

Thanks for the test, and I've experienced mostly the same results.

yahooty..judging from the number of holes in those tree trunks either you have a serious woodpecker problem at that 3D range or a lot of people aren't looking at the target when they release but at the trees they want to miss!!

momentum (p)=mv. kinetic energy (E)=1/2mv^2. velocity is sq important in E and equally important to mass in p. velocity matters in both equations so does mass but mass is more important in p. gpp does not have anything to do with penetration or anything else related to terminal performance of an arrow. It does have to do with how the bow performs which leads to the best performance of a particular set up. penetration simply put, increases as you add mass or add velocity to the set up (all else being equal) mass moving is momentum. based on this you can have a lighter arrow out penetrate a heavy one if its going fast enough to have more momentum (all else equal) ke really comes into play when you get a wave from the impact of the projectile for arrows (or slow bullets like mzlder rb) this does matter from an affect on target standpoint

just trying to get some physics into the conversation

"gpp does not have anything to do with penetration or anything else related to terminal performance of an arrow. It does have to do with how the bow performs which leads to the best performance of a particular set up. "

And this is what seems to be the recurring theme in most of these penetration test. 9-10 gpp seems to consistently be the best performer because that seems to be the best balance point of weight and velocity for most setups. More or less weight seems to take too much velocity or weight, and make the setups less effective.

longcruise. thats called a ballistic pendulum and you can indeed use it to determine velocity energy and momentum.

i suppose if you really wanted to get some a data a shooting machine would be the way to go. or even a crossbow...

Jack Howard did test with exactly the same results over 40 years ago. With any effort you can find links to those test but in short he used three sets of arrows made up for him by Easton that were light, medium and heavy. [actual weights are in the test]. Turns out the lightest penetrated most, then the mediums, and the heavy one penetrated the least.

thats a good article you mention.

Actually Thumper, my test results did not mirror jacks test results. My results were medium, heavy then light. His was light, medium, heavy. Our different results could have had to do with different test mediums, however. Thanks for pointing out that article though, it was interesting

im inclined to believe that test medium has a big effect on results. ive shot light and heavy arrows into dirt and had light arrows go deeper (i was surprised) and ive had really heavy arrows go 2x as deep into foam. i use old pellet bags loosely packed for targets and they stop arrows that drive deep into wood amazing well, they just absorb the arrow and offer little resistance for it to push against. jacks test was well conducted, but i also read a story about him testing with someone on a cow skull and he was perplexed that the light arrows werent getting through it but the heavy ones were. i think bone may be is a different deal entirely

When Fred Bear made his final determination about the 9 - 10 gpp, he actually was doing it with a momentum test.

I don't remember exactly how he did it (wish I could find the article), but here's the jist of it:

He rigged up a heavy block of wood on a rail where it could freely roll/move.

The block had a marker (pencil I think) mounted to it where it would make a graph of each shot.

He shot the block (I think with blunt tips), and recorded how far each shot from different weight arrows moved the block.

He consistently got better results with the 9 - 10 gpp arrows.

Not a penetration test, rather just a delivered momentum test, and we all know the more momentum the arrow has at impact, the better it is going to penetrate.

Rick

that would be an interesting read rick

[[[ "that would be an interesting read rick" ]]]

It is/was. Sure wish I could find it again. It's been a long time since I read it, and there was even some pictures & video of the process.

Rick

Rick if it's the right one. I looked up Fred bear arrow test and it was in 1943 shooting at a bob pendulum. Looked like single wood bows. Interesting test.

So I'm confused do the heavy arrows penetrate more as physics suggest or do the light arrows?

I think a lot of times when lighter faster arrows out penetrate slower arrows in a target medium, it's because of the increased heat the faster arrow generates mildly melting the target and lubricating the arrow allowing the arrow to penetrate farther. I know you weren't shooting 3ds, but this is why sometimes arrows have part of the target adhered to it when you pull them.

[[[ "Rick if it's the right one. I looked up Fred bear arrow test and it was in 1943 shooting at a bob pendulum. Looked like single wood bows. Interesting test." ]]]

Hey Tommy.

Yeah, I somewhat remember that one also. Didn't he get pretty much the same results?

But, the one I'm thinking of was a big wood block on rails. Kinda like a train car. It came after the pendulum test.

Rick

I understand he need to want to see how ones arrow penetrates and compare depths from one arrow setup t another. But is it a fair test shooting into a target that's made to "stop" an arrow as compared to shooting into an animal where the broadhead does all the work basically cutting away soft tissue that's in it's way. Does one walk away from testing into targets with a false confidence how their setup will perform in the hunting field or has professional testing said good penetration into a target equals good penetration/passthru into an animal?

i heard about some ashby guy who did a little work on real animals... just saying

"i heard about some ashby guy who did a little work on real animals... just saying"

So has Bear, Hill, Swinehart, even little old me. And so far, just on deer and hogs at this point, my 9gg shaft has not even appeared to slow down going through an animal. That is also the shaft that did the best in my unscientific penetration test. That is what makes all this interesting, lots of opinions and theories, but even people in the know with lots of testing or real animals come up with slightly results and conclusions.

The only test i have done was on a 1/4 in steel plate with a 45 ACP, 30-30 and a .243. I dont remember bullet weights but the 45 would make a lead mark, 3030 made a big dent and the 243 made a pretty big hole. 243 is a small bullet traveling pretty fast.

I always read these topics, often don't comment. But I do often have to wonder why all the penetration problems, or discussion?

I'll be the first to admit I'm no scholar, and I can tell by the post many of you are much more academically advanced than I am. But i'll be darn, despite not knowing how to calculate momentum or really know what inertia means (or care)..lol

I sure know how to put an arrow through an animal.

penetration = first and foremost a arrow that is flying straight. hence the term "straight as an arrow"

I would say right there is the key to most penetration failure or success.

To often during the excitement of the shot on live game , we fail to achieve that backyard picture perfect form and shot.

So all the effort spent tuning, and all the scientific calculation that went into creating the ultimate arrow, goes down the tube in a plucked string, not reaching anchor, torqueing the string ect...ect..ect..

9-11 gpp from a hunting weight bow....a razor sharp broadhead....and above all remain calm.

shade. everything you say is dead on. without those elements covered youre going to problems eventually regardless of arrow weight

Shade, I agree %100. This was only posted cause the results were different from what was expected. I was actually just testing arrow flight, and that morphed into an unscientific penetration test. As to why there are so many topics on the subject IDK for sure, but i guess people tend to to find the subject interesting. And we are just shooting sticks from sticks, new topics seem to be hard to find haha

There are two topics within this one topic; Results observed by people who have experience shooting arrows into things & results obtained by application of physics of moving objects.

They are both equally relevant. Correct/incorrect observations can be identified by applications of physics. If a chronograph reads 200 fps w/a 500 grain arrow & 150 fps w/a 350 grain arrow you immediately know something's wrong because laws of physics dictate that the lighter arrow should be faster. The same applies to momentum/penetration results.

There is nothing wrong in reading & learning from both experience & science especially if you keep in mind that both can be right or wrong depending on the method & data used to reach the conclusion.

All I know is:

My 9.5 gpp arrows penetrate better into "everything" I have shot them into, than any other arrow weight with the same broadhead.

I've gone all the way down to 7 gpp, and all the way up to 14 gpp, and the 9.5 gpp beats them every time.

If I want better penetration than I am getting with the 9.5 gpp, I'll go up in draw weight/bow efficiency, and bring the arrow weight up to 9.5 gpp to match the new draw weight.

Rick

I wonder if the differences in Physics vs. test results is driven by vary slight differences in arrow tune having a greater impact on penetration then the increase in momentum?

[[[ "I wonder if the differences in Physics vs. test results is driven by vary slight differences in arrow tune having a greater impact on penetration then the increase in momentum?" ]]]

Might be, and probably is at times.

Not on mine though. I bareshaft tune, and fine tune every arrow to my bow before using them to test with.

Rick

Rick ive found your 9 gpp best penetration results to be spot on. This is from my very unscientific, yet carefully tuned setups in the low 40# range.

Good stuff when people explore the capabilities of their equipment!

due to 40 years of psyicle work & psoriatic arthritis in my wrists & shoulders I'm down to 40# or less with trad bows & my personal test is a peice of 3/8 plywood. to me the internal organs present little to no resistance to an arrow it's what the arrow has to punch thru to get inside if you have doughts about your bow beying enough for deer get it tuned the best you can & shoot the broadhead you plan to hunt with hopefully thru a peice of 3/8 plywood & go hunt with confidence

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