Energy loss at various ranges

[SEW]

20" ST 418.6g M405
1yd 369'/sec 127ft-lbs.
20yd 360'/sec 120.
40yd 354'/sec 117.
60yd 337'/sec 106.
80yd 325'/sec 98.
100yd 311'/sec 90.
So from 20 yards to 100 yards only 58'/sec (16%) was lost while only 30ft-lbs (25% )of the energy was lost. More energy was lost due to the speed squared factor of the formula E= MC(2). Any energy above the minimum required (34'-pds) or desired (40'-lbs) for deer (20 more for bear), is just gravy. These energy levels are for "average" fixed blade broadheads. I believe I read a post by Boo stating that once desired energy has been reached, trying to get more energy by sacrificing speed is not desirable. I agree totally. With this in mind, the energy loss of 25% from 20-100 yards is irrelevant since still over twice the energy still remains than is needed.

So, what can we derive from this? First off, my heavily noise/vibration attenuated M405 is just upper mid level performance wise. These shots were all made with a 5-8 mph l-r xwind. The accuracy of the M405/20", 92g insert, 125 Griz Trick, helical Blazers, flat plastic nocks is incredible. Since the M405 is actually sighted in with Lumenoks , I aimed off slightly to help preserve my chronograph . Still I felt comfortable testing out this far. No target practice has been done with this Xbow since mid-September. Its only shots were deer kills. It's still on, even with nearly 20g of difference in the nocks.
Back to the results. Contrary to what many have stated, energy loss seems to be a non-factor even out to 100 yards. Trajectory, range estimation error, and time of flight remain the critical and limiting factors. O.88 sec to 100 yds, 0.51 sec to 60 yds.

Why all this? Because of repeated comments on various forums concerning loss of energy at what many consider "extended" ranges (40-60 yards). I've been repeatedly chastised for shooting at these ranges because "not enough energy" remains for an ethical kill. False!! However, some broadheads can require a tremendous amount of energy to get a passthru (FOCs). After all my promotion of FOCs for higher powered xbows, I've now discontinued their usage in favor of (currently -verdict not in) Grizz Tricks. I want passthru's . I killed a 100#+ doe p(though the picture doesn't look like it's that large) last Fri with a GT(2nd deer of year with this BH). Massive blood trails.

[SEW]

20 yards


40 yards



60 yards



80 yards


100 yards


Doe verses M405/125g Grizz Trick

[Big John]

Very good Sew!
I to have done much testing on the same.
But I gave up arguing with others on it. Life is to short!
I love taking longer shots. Practice heavily, and know what "I" can do. Keep those results and use it to educate as many as you can. As well, I am a Strict user of Slick tricks. But I admit only on Crossbows. I still use mechanicals on Compounds. However, this year I am officially packing in Vert Bow Shooting. Just cant do it without pain. Love reading your testings. Keep fighting the good fight!

Big John

[otisbrazwell]

nicely said now who has a matrix 405 rail they would trade for my 330 rail.

[paulaboutform]

Steve, what a great study! I have to say how much I enjoy your posts and contributions. Very thoughtful, articulate, and informative. I've had the idea to run the identical testing you've done but just haven't been able to pull it together. You've confirmed what I've suspected. Thanks for the excellent intel..

Paul

[ThunderXB]

Steve,

That is astounding work! I appreciate the data!

Do you feel that the 20" arrow significantly out performs the 18" similarly set up arrow?

One reason I ask is that by adding the extra 2" at 9.1 gr per inch you pick up an additional 18.2 gr over an 18" arrow.

I shoot a similar set up out of my 405, except the arrow weight is different, mostly because I am using 100 gr heads & 18" arrows:

18" arrow x 9.1 gr per inch =163.8
100 gr head = 100
92 gr insert = 92
3 vanes at 6 gr ea = 18
plastic nock 8 gr = 8

for a total of = 381.8 gr (Not counting any lighted nock)
with lighted nock = 401.8-411.8 depending on which brand

[SEW]

Concerning length vs added weight: it's just a fact, the longer the arrow, all else equal, the more the arrow planes. It is not dropping strickly with the law of the acceleration of gravity. I like to shoot longer rather than shorter. The BC is better.
FOC really comes into play with longer range shooting. With vbows, especially stick bows, paper testing is important. The best vaneless flight will need the least vane steerage and will deflect the least with broadhead usage. For Xbow usage, we need no, that's zero, flex on launch. Likewise, we need enough FOC to have stable arrow flight to our max desired yardage. What works at 40 may not work at 60, but what works at 60 works well at all ranges below that. Same with what works at 100. More than the minimum of what's need doesn't help any, all it does is cause the arrow to drop faster. I set my arrows up for the least FOC I can get by with and have tight groups at 100. Goal is 1 1/2" at least. My FOC for 100 is greater than what is needed for 60. If I were to only plan on a max range of 60, I'd set up for it and have a lower FOC.
As arrows get shorter, they need more FOC, all else equal. A quill shooting to 60 would need more FOC than an 18" arrow, which would need more than a 20" arrow.
I'm toying with the idea of having an universal arrow for all 3 of my xbows. 19", Lumenoks, 125 Grizz Trick/92g insert or 100g Grizz Trick/110g insert, or hopefully, if it'll group, 100g GT/92g insert or 125g GT/80g insert. I'll also test the highly accoladed G2 fixed blade. My bear fiasco, totally my fault with broadhead selection, has me really BH conscious. I tend to think the angle of the blade is a major penetration factor. Could be wrong. The GT has fairly straight out blades whereas the Wasp 125 XLS, which I use with the Solution(350) have a much lower angle which should penetrate better. Wish I'd used them rather than the FOCs.
More later.

[nchunterkw]

I still tend to shy away from an "minimum required KE" numbers for a particular game animal. There are a myriad of factors that go into making an arrow that maximizes penetration. Flex at impact, work angle of the BH blades, momentum (and how much of it is derived from arrow mass), to name a few. Dr Ashby has done more research on this than about anyone and his work makes great sense to me, and I have tried to adapt it to my setup. Anecdotally, I have killed 3 bison with my crossbows. 2 with my Vortex and 20" arrows and 1 with my Micro and a 16" arrow. While the bows are ballistically almost identical, the shorter (and therby stiffer) 16" arrow had the best penetration of any (complete pass thru) . It weighed right at 500gr, while my previous kill used a 575gr arrow from the Vortex, had adequate penetration but never got the arrow all the way through. What is the momentum of the arrows you are testing?

[SEW]

.0.63 Slugs at 60 yards. This is for that 418.6g arrow. I normally shoot a 447g arrow. I shot an arrow that I think will approximate what most are shooting.
While I realize momentum is more important than kinetic energy, for the game I hunt, I believe I have enough excess energy, I just haven't gotten into momentum. Your situation is radically different.

[ThunderXB]

AND this is why I didn't do well in physics!!

[SEW]

Archery Addict, the only problem I have with the increased FOC causing additional flex on impact is how? If the weight is all in the front of the arrow, why would, how could, thatincrease flex on the arrow behind it? I've always accepted the thought that the heavier front end will penetrate better.
Of course, those of us who have been deeply involved with long range accuracy with vbows, long, recurve, wheeled, thru extreme cams have dealt with spine requirements. Ideally, with a crossbow, no, zero flex, is what we want. Zombies, Spynal Tapps , spine indexed, spine matched, with the least FOC needed is the best we can do. My only compromise on spine is the willingness to shoot a little longer arrows for increased plane.

[SEW]

On launch, effective spine is weakened by weight on the front of the arrow. On impact, forward weight is helpful and doesn't affect spine, at least I don't see how it can. Since you mentioned it, I was a Chemistry/Physics Major, minor in math. By no means, does that make an expert.

[Hi5]

Well, as a history and political science major, I don't understand how additional weight at the front end of an arrow would weaken the spine. That is, on impact, it shouldn't. On launch, yes, definitely.

[nchunterkw]

On launch, effective spine is weakened by weight on the front of the arrow. On impact, forward weight is helpful and doesn't affect spine, at least I don't see how it can. Since you mentioned it, I was a Chemistry/Physics Major, minor in math. By no means, does that make an expert.

Exactly right....I just wrote a big long post about this that went somewhere into the interweb, just not here....


The arrow flexes about the center of pressure (for our purposes the center of the shaft) at launch and during flight. But at impact it flexes about the balance point. High FOC arrows move the balance point forward, so at impact the arrow will flex less because the moment arm of the force is shorter (distance from front of arrow to balance point). Dr Ashby actually advocates "Ultra FOC" arrows to maximize penetration (although his application is on Asian Buffalo) but the concept holds true and can be adapted to our arrows.

Momentum greatly helps penetration as well, but only when it is derived from arrow mass and not arrow speed. Momentum = mass x velocity, so 2 arrows theoretically could have the same momentum, but be of very different weights and travelling at very different speeds. Since an arrow encounters resistance forces at impact that vary with the square of the velocity, the lighter faster arrow will encounter much higher resistance forces than the slower heavier arrow, thus the heavier arrow gets better penetration.

[nchunterkw]

If you put a slow motion camera on a target and see the arrow impact you will see a arrow flexes like crazy on impact. The weaker the spine the more it's going to flex but they all flex. The less flex you have the more penetration you will get. I agree that a arrow with higher FOC will penetrait better than a arrow with lower FOC will. If you have the correct spine to support it but the is a line you can cross where you start going the other way. Crossbow bolts are kinda limited compared to regular arrows. Because with a crossbow bolt spine wise you get what you get there is not a hole lot of options like a regular bow. With a regular bow you can just get a stiffer spined shaft. With a crossbow bolt you don't have as many options so you can't overdue the shaft your useing.

My little Micro with short 16" Zombie Slayer super stiff shafts has absolutely convinced me that you can't go too stiff on a crossbow arrow. It outperforms my Vortex penetration-wise with similar arrows at similar speeds. Main difference is that little arrow is stiffer.