Arrow penetration

[Beendare]

I've also got my own experiences which suggest it's much less about weight and more about arrow flight, a sharp broadhead, and shot placement. Wow. Who would have guessed?

That pretty much sums it up for me too- grin

Well at least the influencers like Ashby and RF have come around closer to more main stream thinking Lately.

It is worth remembering the Snake Oil these guys used to peddle, in Ashbys case it was many years ago. Many of you guys probably won’t remember but Ashby used to claim a very high FOC arrow flies further….and had a “30% FOC threshold”- Laughable

RF used to claim tuning was not necessary admitting he couldn’t tune a bow….and he had a silly chart of Manly arrows stating that the mid 400g arrows millions have had great success with is some Whimpy thing.

Its great that we have some common sense info out there like this vid to counter that crazy stuff.

 

[Wilderlife]

Yeh. The '650gn threshold' is an interesting claim as it doesn't go into any detail about other parts of the system - velocity, overall length/stiffness of arrow, etc.

I've mentioned it in other places on other forums before, that the RF lecture on the Elkshape channel is interesting in plenty of ways, but there are some obvious oversights he brings up that no one seems to call him out on.

He's talking about a heavy arrow and says something like "Aron Snyder is shooting a 585gn arrow! He's obviously come to a similar conclusion!" He neglects to mention anything about it coming out of a 58# recurve, which is the ol' 10gpp setup that is very common in that space. RF wants to talk about KE and momentum a lot so let's have a look at that with some numbers off the internet.

A 580gn arrow doing 180fps has 42 ft lb of KE and 0.4632 momentum.
A 475gn arrow doing 288fps out of my compound has 87 ft lb of KE and 0.6069 momentum.
I've shot 600gn arrows out of my 55# ASL and they're doing 170fps, with 38 ft lb of KE and 0.4525 momentum.

It's not as if an extra 50 grains on my longbow arrows is going to hit some magic sweet spot that defies the laws of physics, and common sense. And, if I shot a 650gn arrow out of my compound, it'd definitely have higher energy and momentum than most trad bows, but the trajectory isn't going to be as nice to deal with.

And I'm not necessarily against 'heavy arrows' either. If I have a trajectory I can live with I don't mind being a little heavier for some things; certainly for most of the game I chase. If I ever go after buffalo or scrubbers I'll bump the weight up some but I'm sure a 525gn arrow at over 270fps would do a great job as a starting point.

 

[Bump79]

I agree on the sharp broadhead point. I won't hunt with it if it won't shave a 3/4-1" bald spot across the entire blade in a single stroke on my arm. My first deer 20 something years ago was a 3 blade large cut mech, 63# draw weight and 315 grain 3d arrow. At 52 yards it blew through her like a hot knife through butter. As I got older the draw weight and arrow weight went up. I stopped sharpening blades. I didn't lose any, but they were making it further with less blood. I started sharpening again and had good blood, and they started dying in sight again. People overestimate the factory sharpness of most broadheads and underestimate the difference it makes.

100%. Even stropping a factory head makes a bigger difference than you'd think.

Yeh. The '650gn threshold' is an interesting claim as it doesn't go into any detail about other parts of the system - velocity, overall length/stiffness of arrow, etc.

I've mentioned it in other places on other forums before, that the RF lecture on the Elkshape channel is interesting in plenty of ways, but there are some obvious oversights he brings up that no one seems to call him out on.

He's talking about a heavy arrow and says something like "Aron Snyder is shooting a 585gn arrow! He's obviously come to a similar conclusion!" He neglects to mention anything about it coming out of a 58# recurve, which is the ol' 10gpp setup that is very common in that space. RF wants to talk about KE and momentum a lot so let's have a look at that with some numbers off the internet.

A 580gn arrow doing 180fps has 42 ft lb of KE and 0.4632 momentum.
A 475gn arrow doing 288fps out of my compound has 87 ft lb of KE and 0.6069 momentum.
I've shot 600gn arrows out of my 55# ASL and they're doing 170fps, with 38 ft lb of KE and 0.4525 momentum.

It's not as if an extra 50 grains on my longbow arrows is going to hit some magic sweet spot that defies the laws of physics, and common sense. And, if I shot a 650gn arrow out of my compound, it'd definitely have higher energy and momentum than most trad bows, but the trajectory isn't going to be as nice to deal with.

And I'm not necessarily against 'heavy arrows' either. If I have a trajectory I can live with I don't mind being a little heavier for some things; certainly for most of the game I chase. If I ever go after buffalo or scrubbers I'll bump the weight up some but I'm sure a 525gn arrow at over 270fps would do a great job as a starting point.

Well said!

 

[doc holiday13]

Yeh. The '650gn threshold' is an interesting claim as it doesn't go into any detail about other parts of the system - velocity, overall length/stiffness of arrow, etc.

I think the "magic 650g arrow" is what they deem "bone breaking threshold"

The biggest qualm i have with their logic is they are focusing their arrows around making a bad shot towards the front of the deer. I've hit the scapula/front leg maybe 1x.. In generally most are prone to hitting further back(liver area) because deer generally walk in a forward motion

I understand that the full pass through is the goal, but you don't need a full pass through all the time. I've had a handful of non pass throughs and saw the deer drop within 50 yards. I will still hold to my postulation that a "perfect shot" isn't defined by pass through, its defined by how quickly the animal dies. In my experience a perfect shot means the animal falls within 50 yards.

 

[Bump79]

I think the "magic 650g arrow" is what they deem "bone breaking threshold"

The biggest qualm i have with their logic is they are focusing their arrows around making a bad shot towards the front of the deer. I've hit the scapula/front leg maybe 1x.. In generally most are prone to hitting further back(liver area) because deer generally walk in a forward motion

I understand that the full pass through is the goal, but you don't need a full pass through all the time. I've had a handful of non pass throughs and saw the deer drop within 50 yards. I will still hold to my postulation that a "perfect shot" isn't defined by pass through, its defined by how quickly the animal dies. In my experience a perfect shot means the animal falls within 50 yards.

This is it! Animals aren't turning their shoulder into you when you shoot (maybe in an extremely rare instance). They drop, roll and turn away from the threat. Completely natural. Add in a step as you mentioned, etc. The entire Ashby/RF principle is based on lethality being limited to penetration being "the" problem. But is it? It's really just one - and it seems to rank fairly low on the list of problems for most people with reasonable setups.

This is an interesting thread I started. Only 7% of people believed that they lost an animal from lack of penetration. The obsession with it does not seem justified given this self reported (while limited) data. Lack of penetration is an easy one to identify too as you see it run off with half an arrow hanging out, find the arrow broke off, etc. The rest aren't so easy to identify often. When it goes wrong for me - I tend to blow through so quick I barely knew what happened and find my arrow and cringe. Arrow indicates gut/stomach. Makes a guy want to quit..



Shops deal with this all the time as well - they hear every hunting story from their customer. This worked, this didn't, this happened, etc. They're actually an extremely good resource as they don't get the online confirmation bias. It's just whoever walks in the door and is representative of their hunting communities experience. Sure they do get some of the marketing hype but that's no different than anything now that everyone is watching Instagram for the latest and greatest thing.

If you're a shop owner/bow tech and the majority of what you hear about is people losing animals from gut shots - then the customer who couldn't shoot a field tip through paper consistently asks what broadhead they should shoot.... what are you going to say? Screw on this massive fixed blade? Or maybe you're going to say man you're probably not going to hit where you aiming.. you might consider shooting this good size cut mechanical for whitetail. That's how we ended up at this location - not because of some conspiracy. It's because we suck - and manufacturers knew it so they supply us what we needed.

Now that the information for tuning, etc. is more available and easily deciphered. Fixed blades are a more popular option again. Which I think is a good thing.

 

[doc holiday13]

So you're reference data for animal loss is interesting for sure.. Here in my area, there is a archery only hunting program in the local parks. I'm sure its under reported but its a requirement for there to be an account for EVERY arrow shot. Miss, Hit, Wound, and Kill. They even require that your arrow be marked with your hunter ID number so if its ever found they can tie it to you.

BUT that report has sections that ask why you didn't recover and where you believe you shot the deer. I'd be curious if that information has been compiled

 

[Bump79]

So you're reference data for animal loss is interesting for sure.. Here in my area, there is a archery only hunting program in the local parks. I'm sure its under reported but its a requirement for there to be an account for EVERY arrow shot. Miss, Hit, Wound, and Kill. They even require that your arrow be marked with your hunter ID number so if its ever found they can tie it to you.

BUT that report has sections that ask why you didn't recover and where you believe you shot the deer. I'd be curious if that information has been compiled

I have seen similar data compiled somewhere - hopefully someone remembers were it is. Cody Greenwood compiled a bunch of data through datakills.com for similar data. There are dog tracking apps out now that are tracking specifically to your setup and compiling it.

It would be great if you reached out to see!

 

[Wilderlife]

I think the "magic 650g arrow" is what they deem "bone breaking threshold"

Definitely. It's just a number they reference. I've read the data they talk about when they bring this up but in more modern times they don't tend to go into detail about other things. I've heard Ed say on podcasts things to the effect of "it doesn't matter about the velocity, etc. We just saw that once you went above 650gn, bones broke easier."

So how are we supposed to take this? What's going to break more bone, with all other things being equal? A 650gn arrow going 100fps, or a 500gn arrow doing 300fps?

That's what gets me caught up with the studies. Again, huge respect for Ed and the work done, data collected, etc. It's an entertaining read and a lot of the information is incredible, but they should be more up front with the points of diminishing returns.

It's like the study Cody Greenwood did on Kifarucast within the last year or so. One of the biggest data points he had was accuracy - those that hit what they were aiming at effectively, were the most successful. Many of the elk shot were around the 60 yard mark. Now I've never shot an elk, and I've never shot an animal further than about 28 metres , but I shoot out to 100m regularly enough, and shoot unknown distances at targets regularly enough, to know that a heavy arrow around the 600-650gn mark out to 'elk hunting distances' is going to be problematic. Hence my current compound setup, being fairly fast. I come from a trad background, so having speed on tap with the wheels now is a nice change.

 

[Zac]

Definitely. It's just a number they reference. I've read the data they talk about when they bring this up but in more modern times they don't tend to go into detail about other things. I've heard Ed say on podcasts things to the effect of "it doesn't matter about the velocity, etc. We just saw that once you went above 650gn, bones broke easier."

So how are we supposed to take this? What's going to break more bone, with all other things being equal? A 650gn arrow going 100fps, or a 500gn arrow doing 300fps?

That's what gets me caught up with the studies. Again, huge respect for Ed and the work done, data collected, etc. It's an entertaining read and a lot of the information is incredible, but they should be more up front with the points of diminishing returns.

It's like the study Cody Greenwood did on Kifarucast within the last year or so. One of the biggest data points he had was accuracy - those that hit what they were aiming at effectively, were the most successful. Many of the elk shot were around the 60 yard mark. Now I've never shot an elk, and I've never shot an animal further than about 28 metres , but I shoot out to 100m regularly enough, and shoot unknown distances at targets regularly enough, to know that a heavy arrow around the 600-650gn mark out to 'elk hunting distances' is going to be problematic. Hence my current compound setup, being fairly fast. I come from a trad background, so having speed on tap with the wheels now is a nice change.

Ed could be right regarding velocity. It’s such a fickle parameter, and is easily the most quick to dissipate. I could be wrong, but I don’t think 20 or 30 fps amounts to much as far as penetration goes. Anyone that hunts with a stick can verify that a shaft traveling at a whopping 170 fps can slice through anything.

 

[Wilderlife]

For sure, but there would still be a point of diminishing returns.

Another example is the fact that you see very similar numbers for KE and momentum when you raise or lower the arrow weight. I'm not sure at what point things cross over and you see bigger changes, but even 50gn more or less weight on my compound arrows sees the numbers stay very similar. Obviously the velocity changes a lot, but the KE and momentum don't change as much as you'd expect, which goes back to the points being made about trajectory being a big factor in confidence and effectiveness when hunting.

Some examples - using a different calculators, etc, so take with a grain of salt.

My 475gn arrow going 288fps has roughly 88 ft lb of KE and 0.6 momentum.

If I bring the arrow weight right up to 650gn, it estimates 230fps, which gives me 76 ft lb of KE and 0.66 momentum.

Before anyone says anything, YES, I know that RF argues that heavier arrows will retain more velocity down range so out to a long distance you may see things crossover, but I don't shoot animals really far so it makes no difference to me. Is 0.06 gain in momentum statistically significant? I'm not sure. Maybe some people could argue either way, but it would be impossible to argue that a trajectory starting at 230fps is as nice to hunt with as one starting at 288fps.

That's what I believe RF is missing when he talks to a lot of these people shooting a reasonable distance. Is anyone out there genuinely going to want to see a DROP in KE and an inferior trajectory, all for a 0.06 gain in momentum? Even if those numbers were more significant with the arrows at 40 metres, the chance of hitting something at 40 metres is far lower with the slower arrow.

Now back to his comments about Aron Snyder shooting 585gn but not acknowledging it's coming out of a recurve.

If we say 180fps, we get 42 ft lb of KE and 0.46 of momentum. We all know that 585gn out of a recurve doing 180fps is more than enough to kill most things, but using a data point like that in the heavy arrow argument is pointless when an arrow roughly 90gn lighter has a stack more energy and momentum.

I don't know when I turned into the sort of bloke who crunches numbers, but here we are. I understand a lot of what has been driving this discussion is the fact that you see a lot of white tail hunters up there shooting expandables and struggling to get decent penetration, but the numbers suggest it has more to do with arrow flight and tune than anything else?

 

[ozyclint]

Don't forget to consider that slower objects encounter less resistance. Your slower arrow example not only has .06(insert units here) more momentum but it also encounters less resistance.
Resistance increases as a square of the velocity. Double the velocity= 4x the resistance.

 

[entropy]

My 475gn arrow going 288fps has roughly 88 ft lb of KE and 0.6 momentum.

If I bring the arrow weight right up to 650gn, it estimates 230fps, which gives me 76 ft lb of KE and 0.66 momentum.

I am pretty sure that the above cannot be correct. A bow is a constant kinetic energy launcher. It doesn't matter what weight arrow you shoot, your KE will be roughly the same, because the same amount of potential energy in the limbs is available. Going to a heavier arrow typically yields a slightly higher KE value, because the bow is able to use energy more efficiently on a heavier projectile, so doesn't waste as much energy to noise/friction/etc.

I have personally found the online calculators to be pretty worthless, particularly as you go up in arrow weight.

 

[Wilderlife]

That's the point I was trying to make, and I did mention to take the calculations with a grain of salt. There would also be a point where a cam becomes less efficient than it could be in other spots and this might have to do with draw lengths, arrow weights, etc. It's one of the reasons why Mathews have the module system, so they can have maximum efficiency at particular draw lengths and poundages, but it becomes a pain in other areas.

My KE is very similar anywhere between about 450-530gn, which is why I suggested people may make decisions about gear based on a trajectory they are happy/comfortable with above most other things.

The stuff ozyclint brings up about resistance is obviously valuable as well, but again, a point of diminishing returns would be there.

Obviously a super fast 350gn arrow isn't going to be desirable for a variety of reasons, but a super slow 650 grain arrow may be similarly undesirable, but for completely different reasons. That's all this thread is getting at, IMO.

 

[billysmals]

I also wonder what the flight trajectory difference is between the 450/600/705 arrows. It matters to me the ARC required to achieve similar points of impact. The tree branches at 30 yards and 20ft in the air aren't always noticeable when looking down hill at a screaming bull 60yards down range making you crap your pants. That matters, which is why I changed to shooting with both eyes open to try to take into account the arrow path, but even then I have no idea if I should be looking 10ft, vs 15ft, vs 20 ft in the air looking for clearance for my arrow. A difference between those arrow weights of something like 2 vertical feet is not a huge amount, but it could be like 6 feet or more ARC required for those arrow paths....that's a lot... I think most people look around the target, but how many of you know what rough vertical feet you should be examining for your arrow flight? It scales as you get farther away of course...it matters less at 20yards, but 60 yards.....it's a big deal.

Also how can a 600gr arrow and a 705gr arrow only drop a difference of .10 inches at 60yrds? The video he posted showed a 9.7 drop for the 600gr and 9.8 drop for the 700gr. I get that cams are efficient, but that this seems like a statistical variance that can't be accurate? Maybe I misunderstood? I rewatched the video to confirm I had it right, and that's what was listed....I have never ever seen a modern compound bow shoot arrows of that big weight variance anywhere close to the same speed to create a drop variance of .10 inches....I have seen like some 480 and 460 arrows shoot similar and some 500-525, but 100gr's is a huge difference. Anyone seen that before?

 

[MattB]

I am pretty sure that the above cannot be correct. A bow is a constant kinetic energy launcher. It doesn't matter what weight arrow you shoot, your KE will be roughly the same, because the same amount of potential energy in the limbs is available. Going to a heavier arrow typically yields a slightly higher KE value, because the bow is able to use energy more efficiently on a heavier projectile, so doesn't waste as much energy to noise/friction/etc.

I have personally found the online calculators to be pretty worthless, particularly as you go up in arrow weight.

The bolded has been my finding in every case when I have experimented with varying arrow weights out of a given bow (e.g. 350 grs up to 650 grs). If memory serves the KE difference was only 3-5%.

 

[Billy Goat]

In my playing with heavier arrows and fps, I was seeing 3/4" for 10 fps (30 grs) at 40 yards.

Didn't go much further, but that was with a shooting machine.

 

[entropy]

The bolded has been my finding in every case when I have experimented with varying arrow weights out of a given bow (e.g. 350 grs up to 650 grs). If memory serves the KE difference was only 3-5%.

Same here. Had to dig for this a bit, but I bought that RF test kit Ethics used to sell a few years ago and chronoed the arrows I had at the time with all nine field point weights. I didn't get KE differences that big... less than 2% between the lightest and heaviest arrow. Only three shots per weight, and there was more variance in the velocities than I would have liked to have seen. Some of the arrow weights spit out all three readings within 1 fps, others there was 3 fps difference between the slowest and fastest for that arrow weight. Wish I could have done this with the Labradar I borrowed last year. Anyway, the table is below, and though there are hiccups likely due to an imprecise speed measurement device, the trend definitely goes in the direction of more weight gives more KE.

TAW	Avg fps	KE ft-lb
516	292.7	98.2
541	285.3	97.8
566	279.0	97.9
591	274.0	98.5
616	268.3	98.5
641	264.7	99.7
666	258.7	99.0
691	254.3	99.3
716	250.7	99.9

 

[MattB]

Same here. Had to dig for this a bit, but I bought that RF test kit Ethics used to sell a few years ago and chronoed the arrows I had at the time with all nine field point weights. I didn't get KE differences that big... less than 2% between the lightest and heaviest arrow. Only three shots per weight, and there was more variance in the velocities than I would have liked to have seen. Some of the arrow weights spit out all three readings within 1 fps, others there was 3 fps difference between the slowest and fastest for that arrow weight. Wish I could have done this with the Labradar I borrowed last year. Anyway, the table is below, and though there are hiccups likely due to an imprecise speed measurement device, the trend definitely goes in the direction of more weight gives more KE.

TAW	Avg fps	KE ft-lb
516	292.7	98.2
541	285.3	97.8
566	279.0	97.9
591	274.0	98.5
616	268.3	98.5
641	264.7	99.7
666	258.7	99.0
691	254.3	99.3
716	250.7	99.9

Your mass range was 200 grs and mine was at least 300 and maybe a bit more (did the work 10-15 years ago, can’t recall if I topped out at 650 grs or perhaps 710 grs), so me getting a more significant KE % difference would make sense. But I think the salient point is the difference is really not that significant.

 

[Billy Goat]

Same here. Had to dig for this a bit, but I bought that RF test kit Ethics used to sell a few years ago and chronoed the arrows I had at the time with all nine field point weights. I didn't get KE differences that big... less than 2% between the lightest and heaviest arrow. Only three shots per weight, and there was more variance in the velocities than I would have liked to have seen. Some of the arrow weights spit out all three readings within 1 fps, others there was 3 fps difference between the slowest and fastest for that arrow weight. Wish I could have done this with the Labradar I borrowed last year. Anyway, the table is below, and though there are hiccups likely due to an imprecise speed measurement device, the trend definitely goes in the direction of more weight gives more KE.

TAW	Avg fps	KE ft-lb
516	292.7	98.2
541	285.3	97.8
566	279.0	97.9
591	274.0	98.5
616	268.3	98.5
641	264.7	99.7
666	258.7	99.0
691	254.3	99.3
716	250.7	99.9

Might not apply, but when shooting something I know is weak or very weak, I have had a fair amount of variation over a chrono. I figure that shaft is flexing pretty good.

At around 7-8 gr per # with good spine, I generally get very consistent velocity. Like .3 variance over 3 shots.

 

[Bump79]

Also how can a 600gr arrow and a 705gr arrow only drop a difference of .10 inches at 60yrds? The video he posted showed a 9.7 drop for the 600gr and 9.8 drop for the 700gr.

He had an error there for sure. He didn't recalibrate the software.