Tested Arrow Speed and Weight - More data

[cnelk]

This afternoon I ran some different arrows and weights thru my chrono for speed and testing.
And I thought the results would be interesting to share.

Equipment:
Bow
2013 PSE Drive
57#

Arrows
GoldTip Hunter XT 55/75
27.5"

360gr - 270fps - 58.29lb of KE

385gr - 261fps - 58.25lb of KE

400gr - 256fps - 58.22lb of KE

425gr - 250fps - 59lb of KE

445gr - 245fps - 59.33lb of KE

[ElkNut1]

My question is, what are you doing drawing a bow already???? (grin) Does your Doc know? Those are great speeds for 57#

ElkNut1

[buglmin]

What catches my eye the most is the loss of arrow speed compared to the small amout of KE gained...85 grains in arrow weight difference, 35 fps lost, and not even a pound of KE gained...

[cnelk]

buglmin

I was most surprised by the same thing!

[Swede]

25 ft/sec may seen significant, but I expect you will see that difference diminish at 30 to 40 yards.

[cnelk]

Paul
My hand surgery isnt for 2 more weeks.
Living high until then!

[mtnmutt]

KE = (M x Vsquared) / 450,240

KE = (Arrow Grains x fps x fps) / 450,240

The fps appears to have a larger influence on KE.

I do not know how to calculate Momentum, however some believe that it is more important than KE. I haven't got a clue and I don't want my brain to work that hard. KE is easier.

[buglmin]

I dunno what magic bow/arrow combination youre shooting, but 25 fps is a huge number to overcome, period! Set up your bow to shoot 25 fps slower, leave your sights set and tell us how bad you miss the target at 40 yards...Sometimes giving up arrow speed isnt worth what is gained in KE, which is usually very little gained. something I have argued for years...

[HurricaneHuge]

I'll take penetration over speed any day. Speed killing is myth in hunting. A heavy arrow will carry more momentum and quiet a bow down significantly. I'm much more worried about noise than speed. I'm not snap shooting long distances. Even 40 yards isn't a quick decision unless I have ranged land marks prior. A quiet shot at 40 yards will be much more productive than a fast, loud shot at the same distance. But I shoot a 480 grain arrow at 80 lbs. so my definitions of heavy and quiet are different from most.

[cnelk]

If I get a chance later today, I will shoot the lightest and heaviest arrow from 40yds and note the difference in POI.
Once I determine that, I will get a chrono reading at 40yds and document that difference too.

Stay tuned

[ElkNut1]

Brad, thanks, sounds good! Probably 12" of drop.

mtnmutt, do not over think your setup, 50# with a 400grn arrow will have no issues on an elk out of your compound, just hit them where they live!

Here's a photo of a bull my son took with a 40# Hoyt Raider with a 400grn arrow & 3 bladed head to boot.

ElkNut1

[Freebird134]

KE = (M x Vsquared) / 450,240

KE = (Arrow Grains x fps x fps) / 450,240

The fps appears to have a larger influence on KE.

I do not know how to calculate Momentum, however some believe that it is more important than KE. I haven't got a clue and I don't want my brain to work that hard. KE is easier.

Momentum (p) is just p = m·v where m = mass and v = velocity

This test illustrates just how misleading KE can be. Everyone is so caught up in KE--it's become just something else to brag about that "mine is bigger." Intuition tells us that even though cnelk's 360g arrow and 445g arrow have almost the same KE, the 445 would penetrate more (and probably also be more forgiving, more stable, and all around better at longer hunting distances--all else being equal, of course).

The momentum for the lightest and heaviest arrows then are:

360g x 270fps = 97200 g·f/s
445g x 245fps = 109025g·f/s
*(Note: I've always seen archers present momentum without units, and it's usually a small number less than 1.0. I don't know why. They must convert to metric or something. It just isn't necessary to convert as long as the units are standardized, and we archers always use grams and feet per second. Unitless numbers drive me crazy!!!)


So you are getting about 12% more momentum with the heavier arrow. What does that mean? Well, honestly I don't know. Is 12% more momentum good? Thats for you to judge. The other caveat is that these speeds (and thus momentum) are determined at probably less than 5 yards. I really enjoy playing with archery programs that can predict arrow speed/ke/momentum/etc at a given distance like the software from pinwheel. My my new bow, here is some numbers at 0 and 65yards:

0 yards: heavy arrow has 16% more momentum
465g @ 297f/s = 138105 g·f/s
365g @ 325f/s = 118625 g·f/s


65yards: heavy arrow maintains 19% more momentum
465g @ 269f/s = 125085 g·f/s
365g @ 288f/s = 105120 g·f/s


Possibly these are extreme examples, since the arrow weights differ by 100g. For me, it is a no-brainer: besides the other benefits of a heavier arrow, ~20% more momentum for a longer shot is pretty convincing!

[Freebird134]

Brad, thanks, sounds good! Probably 12" of drop.

mtnmutt, do not over think your setup, 50# with a 400grn arrow will have no issues on an elk out of your compound, just hit them where they live!

Here's a photo of a bull my son took with a 40# Hoyt Raider with a 400grn arrow & 3 bladed head to boot.

ElkNut1

I agree entirely that shot placement is the biggest factor. But, "do not over think your setup" .... you are crazy Paul!!! Outside of hunting season my favorite thing is to "over think" my setup! Tinker and daydream is what keeps me sane until Fall!!!! (which you can tell by my previous post!)

[mtnmutt]

I am going with Paul's advice. I will build about a 400 grn arrow. As long as it tunes to my bow and flies well, I am done. I would rather spend my time practicing and not tinkering.

cnelk and Freefird134 may have the elknut award for tinkering. I noticed how Freebird134 made a claim to being sane. I won't touch that one. After all, this is a civil forum.

[cnelk]

Didnt get a chance to shoot tonight.
Had a slight drizzle of rain today so I met an ol buddy for a couple beverages and Rocky Mtn Oysters.
He been going thru some tough times and it was good to hook up and chat

More to come...

[cnelk]

OK
Got back out to do some more testing.

I only shot two different weights of arrows from the same bow
The 360gr and the 445gr

At 40yds the POI was 8 inches different

At 40 yds these were the results thru the chrono

360gr - 234fps - 43.78# KE

445gr - 213fps - 44.84# KE

Also
There was just a slight breeze from left to right that drifted the 445gr arrow more than the 360gr - only ~2in tho

Thoughts?

[buglmin]

85 grains in arrow weight difference, 21 fps lost by the heavier arrow, only 1.14 # of KE gained, 8" lost in trajectory...all for only a lil over a pound in KE...and 2" at forty yards could be a huge thing shooting through the trees...and yessir, Im enjoying shooting my compound again...having thought of picking up the curve in over a week...I really just be sick!!

[Swede]

Cnelk your information cooresponds very closely to what I observed several years ago when I was doing some testing. We have used different bows and different arrows I used a 500 gr. arrow and a 350 gr. arrow. I found the lighter arrow lost 6 feet per second more speed at 40 yards than the heavier one. You show a 4 ft / sec difference.

[ctdad]

freebird,

I don't really disagree with the potential importance of momentum. However, you admit that you don't know if 12% more momentum is a good thing. Here lies the debate. While KE may be over analyzed by archers, implying that momentum is more important without any reasoning why isn't very fair.

Also, adding intuition into a math equation isn't fair either.

I don't mean this to start an argument. I was actually glad someone mentioned momentum as I think it is probably very important in the discussion. I just felt like you were very pro-momentum and a little bit anti-KE, though I can't be sure why.

Personally, I've never had penetration cost me an animal. I've had poor shooting and shot placement cost me a few, so I focus more on that. Some will argue the two can't be separated completely. Great discussion.

[Swede]

I have had penetration issues on long shots with light arrows. I am not one to use heavy arrows even today, but I have increased their weight to 420 grains. For years I shot arrows that were less than 360 grains total. I got many kills including complete pass throughs on elk. The trouble I expereinced was at 40+ yards. When I hit a rib, the arrow did not penetrate enough. I watched my arrow hit a deer in the side on a long uphill shot. I heard the crack of a rib. When I got up to the place where the deer had stood I found the arrow with only about one inch of the broadhead showing blood. I had the same experience with elk. As a consequence of that, and having animals move, I have limited myself to 40 yards.

[pointysticks]

any thought on "where" the arrow weight is? say two arrows weight the same 450gr...but one has 15% FOC and the other a 11%..

i've read that the higher FOC will have better penetration, but cannot prove or disprove this.

[Freebird134]

ctdad,

I think you are dead on that accuracy/placement is more important than either KE or momentum values! Most of us are producing way more energy than we really need to kill anything in N. America. I like heavy because I find it more accurate in a hunting situation (eg, forgiving, wind drift, etc). Not because it penetrates better.

Truth is that I don't know which is more important, KE or momentum. I didn't mean to be anti-KE, but maybe that's the way it came across. Actually, upon further digging, it seems like KE actually might be more appropriate and important in a hunting situation than momentum (at least according to physicists). I guess Ashby is responsible for pushing the "Momentum movement," or at least that's the impression I get. He talks about it in his reports on penetration. He also uses a lot of physics equations in those reports ... but actually it seems he misuses them. I don't entirely understand it all and have had some physics buddies try to help me. The gist of it is this: Ashby's conclusions that momentum is more important based on physics theory is misguided because those equations have the assumption that an object is moving through a fluid (air or liquid), and the conclusions do not apply to an object moving through a semi-solid. Talking to my physics friends and (for what it's worth) online physics discussions, those guys are leaning towards KE being more important that momentum! I'm confused!!!!

Here is a link to some physicists nerding out on archery if you are interested in their forum discussion: http://www.physicsforums.com/showthread.php?t=195119

It's fun for me to think about this stuff and consider how weight, speed and energy affect hunting performance, but in reality any hunting arrow out of a modern compound will do it's part if you can place it behind the shoulder.

[ElkNut1]

Cliff, with equal wt arrows yet one has a heavier head wt, that heavier head wt arrow will out penetrate the lesser head weighted arrow. I've tested this on several occasions. The thing that doesn't change much is the arrows impacting the target! I tested two arrows as you are talking about out to 50yds, they hit the same height. These were two 390grn arrows, one had a 15grn insert & 100grn head & the other had a 65 grn insert & 125grn head. So two arrows of equal wt, one had a 115grns head wt & the other 190grn head wt. here are the results after multiple shots all were similar penetration, the one with the white cresting is a 429grn arrow so focus on the other two, look at the penetration difference, the heavier head wt arrow penetrated best. The 2nd photo is a 50 yd shot with the two 390grn arrows with two different head wts, note they hit the same height.

ElkNut1

[buglmin]

Paul, while I agree that an arrow wuth higher foc will penetrate a lil better, I keep mine around 14% for both compound and recurve, but why two totally different arrow set ups for your test?
One arrow has short blazer vanes, while the other has 5" feathers on a GT shaft...The blazers are actually faster then the feathers because of less wind resistance, and the fact that slo mo video has showen how feathers flap in flight, reducing arrow speed. Would the results been less dramatic if both arrows were fletched the same? Just asking, cause curious minds wanna know...

[ElkNut1]

Anthony, good question. Those tests were all done with a 65# compound bow. I had many different arrows I used during all the testing, mostly of stuff I had around. Then I had other hunters send me quite a few different other arrows as well, I tested most of them from skinny VAP arrows to the fattest Victory arrows. I tuned them all to the bow before testing. In order to do this some had tubes & different things added to the arrows to meet weight. As far as the different fletchings used it didn't seem to make any difference in penetration or speed, the weight of the arrow was the determining factor in nearly all shots made.

Look closely at the 50 yard shot & you'll both those arrows hit within an inch of height even though the Gold Tip has one feather & two fletchings, speed was really not affected or it would have hit the dirt well ahead of the target. It was that way because I used to shoot all my arrows that way just to be different. (grin) I have plenty of arrows that were the same that I tested where results were the same, arrow weight or tip weight was the determining factor in penetration.

But to answer Cliffs question I did not find arrows of exact wt. differ because one had more tip weight than the other.It was so close to the same it was a non issue. Maybe it would show up more at 80yds plus?

ElkNut1

[buglmin]

Thanks Paul, and after looking at the picture with your son and seeing one of you now, you havent aged a bit...lol
Its fun to read some one elses opinions and thoughts on arrow weight, like nowing guys are never too busy to take the time and play with their equipment, think everyone should be experimenting instead of taking someone elses advice as the "Book"...

[cnelk]

Of all the options I shot in the test, which one would you recommend or use?

They all shot great out of my bow which is tuned quite well...

[buglmin]

Man, this is a personally thing, something youve got to to play with and decide. Whatever your choice, youve got to have the confidence in your arrow that it'll do what you need it to do.
Are you planning on staying at 57#, or increasing bow weight as soon as you can? That will factor in arrow weight and design...

[ElkNut1]

Anthony, that photo was many moons ago my friend! My son will be 35 in Aug, he was 13-14 there. I think I was about 137# I now am 155# but still in some sorta elk shape. (grin)

cnelk, I agree all those arrows can be tuned well to your bow, it's all about matching the arrow spine. Out of your 57# draw the 400grn arrow will most likely offer the best penetration in either a .400 or .340 spine, the 425grn would be a very close 2nd but could catch up in penetration in shots to 40yds plus.

Here's 2 photos to help with your thoughts. These tests would apply in your case as well but considering your 57# draw wt. Remember I shot these out of a 65# Hoyt compound bow. For my poundage the best penetrator was the 429grn arrow or something close, everything 25grns heavier or lighter lacked in penetration when compared in the testing. The lighter arrow is 406grns & did not penetrate as well. Notice in the 40yd shot the 406grn arrow did not make it through the cement board, it's hanging on by a thread, it nearly bounced out. The 429grn arrow went through all the layers & into the target. Yet, we are only talking 25grn difference in arrows! These are identical arrows shot here.

Too, you'll notice the 429grn arrow has 2 fletch instead of 3, I shot that arrow over 100 times into that cement material, it flies like a dart! (grin)

ElkNut1

[ElkNut1]

Now if we go to the heavier than 429grn arrow out of the same 65# bow to a 472grn arrow see what happens at 30yds & 40yds. Many hunters feel that the heavier arrow will always penetrate better, but at hunting distances this has not been the case in any of the testing I've done. Each bow has a peak, when it is reached things can decline with too light or too heavy, we've seen too light up above for a specific wt. & now look at too heavy for this specific draw wt.

The FMJ is the 472grn arrow, it has the less penetration.

ElkNut1