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#1 Spirithawk

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Posted 13 October 2010 - 04:44 PM

Can someone settle an argument for me? Seems I've always been led to understand that a arrow shot from a crossbow loses energy faster than one shot from a verticle bow due to the shorter, lighter shaft and shorter power stroke than that of a vertical compound bow.? Is that correct or not?

Edited by Spirithawk, 13 October 2010 - 06:33 PM.


#2 TerryfromAR

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Posted 13 October 2010 - 06:53 PM

Norm that's what I always heard, and it makes sense when you think of Newton's First Law... "An object in motion will tend to stay in motion unless acted upon by an unbalanced force." The 2 forces that you have acting upon it are the resistance of the air around the arrow, and gravity. The air slows the arrows flight, and gravity pulls the arrow towards the ground. Now we switch gears and start thinking about velocity x mass= momentum which is the formula for calculating energy. The more momentum, the less energy the arrow/bolt loses. An arrow weighing 150 grains will lose momentum twice as fast as an arrow weighing 300gr when the same amount of force is applied in the same direction.

In other words, if they won't listen to common sense... confuse them with mathematical equations.. LOL
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#3 Jeremiah

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Posted 13 October 2010 - 07:45 PM

The problem is... Most crossbow bolts weigh just as much as typical hunting arrows shot out of a compound.
Additionally, it seems many modern crossbows are throwing those bolts at similar velocity to many modern compound bows.
(Truthfully, many crossbows actually shoot a little faster thus generating a bit more energy. But, as a whole, the ballistics are very similar.)

As an example, my current crossbow and old compound were both shooting bolts and arrows respectively of approximately 400 grains total weight.

With mass and velocity being the two key components whether calculating for Kinetic Energy or Momentum, again, I've found that typical hunting set-ups (both compound and crossbow) are ballistically very similar.

Now, there are other factors that do come into play with a typical bolt being shorter than a typical arrow.
One: Rather unrelated to flight, it seems to take about double the draw weight to propel a crossbow bolt ballistically similar to an arrow shot from a modern compound bow. (Generically, the power stroke on a typical crossbow is about half of that on a typical compound bow; about 12" to 15" vs. 26" to 30".) This fact makes for a much more "violent" launch when a crossbow is fired which, of course, causes much of the louder noise they have. (Remembering again that the crossbow is shooting around 2.5 grains of bolt weight per pound of draw weight whereas most compound bows are shooting 5 grains of arrow weight per pound of draw weight or more.) This is also the reason why some crossbows require "special" broadheads, for example, if shooting mechanicals. (Basically a beefed up blade retention system so that they don't deploy at the shot.) It's not the velocity, which many people mistakenly believe, it's actually just the initial launch force.
Two: Specifically concerning flight, we do see that the shorter bolt is simply less stable in flight than a longer arrow. Honestly, you would be best served to research rocketry to find the actual principles behind it. But, I can say from personal experience that bolts seem to become erratic in flight sooner than an arrow and this can lead to premature shedding of down-range velocity and energy.

Well, far from exhaustive. But, that touches upon what I imagine the argument may have entailed. It's really one of those things where on the surface the two are pretty equal. But, when you begin to factor in the real-world issues (again, rocketry is a wealth of info on arrows - no laughing :P ) you do begin to see some discrepancy. (Just not for the reasons most people assume!)

I'd put my money on Leo to have something to add about the real-world physics involved as well.

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#4 Spirithawk

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Posted 13 October 2010 - 08:04 PM

Thanks guys. Jerimiah, boy you nailed it. Anyone wants a wake up then just shoot a crossbow in a food plot or field where you can watch it fly. I also found this info on Ten Point Crossbows site;


Myth: A crossbow shoots much faster and farther than compound bows.

Fact: Under controlled conditions, a series of velocity and kinetic energy tests were performed on two compound bows with 70# peak draw weights (248 and 205 feet per second) and 2 crossbows with 150# peak draw weights (228 and 242 feet per second). The bottom line was that both the compound bows and crossbows produced similar ballistic results. That is, the crossbows did not shoot farther or faster than the compound bows.

If anything, the crossbow begins to lose velocity and energy slightly faster than the compound bow after 30 yards because it shoots a lighter/shorter arrow. However, that difference, while measurable, is slight and insignificant considering the typical whitetail deer shot is less than 30 yards. Also, crossbows produce less kenetic energy than compounds due to the much shorter power stroke.


Now, that being said it seems reasonable that if you increase the distance, beyond 30 yards, you therefore increase the differance in velocity and energy and it's significance. Clear as mud? :lol:

#5 Leo

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Posted 13 October 2010 - 08:32 PM

Jeremiah brings up a great point about stability. Terry you are right to bring up the rate of momentum transfer.

Stability is a real eater of downrange velocity. If that tail starts wagging on the arrow or bolt. The amount of area for air to push on increases dramatically. The result is an increased rate of momentum transger. This slows down unstable projectiles rapidly.

Maybe things have changed. It used to be extremely difficult to get any offset or helical fletchings to work on crossbow bolts (if at all). I believe that is because of the requirement of putting the "C o c k" vane down in the rail. I'm not real up to date on crossbows. I think you can get away with a little more offset now but I don't have a clue how much. The lack of spin imparted to the bolt by the fletchings really hurts downrange stability. This is especially true on shorter crossbow bolts. Heavier weight heads do help stability. This is because then the bolts have a higher FOC. The higher FOC gives the vanes a larger mechanical advantage to stabilize the bolt.

It's not Rocket Science... OK Jeremiah... I kinda agree... it actually kinda is :)

Edited by Leo, 13 October 2010 - 08:35 PM.

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#6 Jeremiah

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Posted 13 October 2010 - 11:51 PM

Excellent points all around.

I've found that a lot of it is relative and really comes down to the specific equipment involved.

My Excalibur crossbow, for example, can easily handle up to about a 6 degree straight offset on a 4" vane. While not a true helical, this does seem to provide enough stabilization to make a bolt fly pretty well out to about 50 yards with a mechanical broadhead, in my target shooting experience. (Do note that I regularly shoot my current compound bow out to 70 yards with similar accuracy results to that of the crossbow at 50 yards during target practice. So, don't anyone get any ideas about "hating" on the crossbow just yet. :lol: ) Some crossbows today still have a narrower channel that does not allow for much more than about a 2 degree offset on the fletchings, however. (Especially if still using 5" vanes which some crossbow manufacturers still recommend.) Obviously, we are just getting back into the issue of stability, or lack thereof, causing premature velocity and energy loss there.

Another simple, but often overlooked, factor is how "true" the crossbow is being drawn. If the string is off center at all it would be the same as moving the nocking point on a compound bow up or down the string from shot to shot. This is obviously detrimental to accuracy as it "pushes" the projectile in one direction or another. (To me, this is still the biggest disadvantage to a crossbow. Nothing short of a cocking device, be it a rope-style or mechanical, and placing marks on the serving that allow you to see that the string has been drawn true can really allow a crossbowyer to achieve a consistently high level of accuracy.)

As I touched upon earlier, my crossbow shoots a ~400 grain bolts at ~325 feet per second. This is a good 40 f.p.s. faster than my old compound used to shoot a ~400 grain arrow. So, specifically in this case, my crossbow actually generates close to 22 ft/lbs more Kinetic Energy than the compound bow did. Combined with the velocity advantage and good bolt stability, my crossbow would outperform my previous compound bow at just about any distance I shot (ballistically speaking). My current compound bow is much closer to the crossbow, however, only being edged out by approximately 10 ft/lbs of Kinetic Energy which is more negligible. If I looked at my dad's older Barnett Quad 300 crossbow, however, his numbers would actually be well below that of my current compound. (Possibly even below my old compound. I would need to run his number again as I do not recall them at this time.) Which just brings us back to the relative nature of the discussion.

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#7 TerryfromAR

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Posted 14 October 2010 - 05:19 AM

Jere, an old trick I found somewhere ( I think on the video that came with my crossbow so many years ago) if your center serving is not black or too dark to do it... you can use a marker to mark the center serving on either side of the rail to help ensure you have drawn the string back straight.... If it is a black or very dark center serving I've found liquid paper works well... Just a thought...
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#8 Leo

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Posted 14 October 2010 - 10:31 AM

Jeremiah stated that the crossbows are ballistically very similar to verticle bows. It's true but a lot of folks don't believe it.

One of the most common misconceptions about crossbows is about their relative power when compared to a verticle bow.

On the surface, reasoning a 150lb crossbow is twice as powerful as a 75lb compound seems reasonable and logical. It simply isn't as straight forward as comparing draw weights.

Here is a crude example to illustrate the point.

A 75lb draw weight bow with a 24inch(2 ft) power stroke versus a 150lb draw weight crossbow with a 12inch(1 ft) powerstroke.

If the loading curve for each bow is flat(which they aren't). IE. Every inch of powerstroke is at full draw weight. The potential energy stored in each bow is the product of the draw weight (in lbs) times the powerstroke (in ft).

So that means the bow has 75lbX2ft=150ft-lbs and the crossbow has 150lbX1ft=150ft-lbs of stored potential energy. The potential energies are the same!

This potential energy is the absolute maximum energy transferrable to the arrow. In other words neither bow can deliver an arrow at a higher kinetic energy than the energy actually stored in the bow.

The efficiencies of each platform determine how much energy gets stored and ultimately transferred to the projectile.
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#9 Spirithawk

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Posted 14 October 2010 - 12:05 PM

Thanks guys. I really value your input. I tend to try and simplify things but doesn't this make sense or am I seeing things wrong?

Ok, lets take two identical arrows. Both 28". Cut one down to 20". Add identical broadheads to both. Doesn't it seem that the shorter arrow would then be lighter than the longer one? That being so, if both were fired at the same velocity, wouldn't it seem logical that the shorter arrow would lose energy faster? Of course that can be over come by adding a heavier broadhead to the shorter shaft but it still shows the length of shaft does make a differance.


Edited by Spirithawk, 14 October 2010 - 12:10 PM.


#10 Leo

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Posted 14 October 2010 - 12:39 PM

Thanks guys. I really value your input. I tend to try and simplify things but doesn't this make sense or am I seeing things wrong?

Ok, lets take two identical arrows. Both 28". Cut one down to 20". Add identical broadheads to both. Doesn't it seem that the shorter arrow would then be lighter than the longer one? That being so, if both were fired at the same velocity, wouldn't it seem logical that the shorter arrow would lose energy faster? Of course that can be over come by adding a heavier broadhead to the shorter shaft but it still shows the length of shaft does make a differance.


Here is what physics tells us would happen given those conditions.

1. The lighter arrow would have less momentum and less energy than the heavier arrow launched at the same speed.
2. Because the rate of momentum transfer is influenced by speed and everything else is equal the rates of momentum transfer and energy transfer would be the same! This does not mean they will perform the same.
3. The lighter arrow cannot produce the same amount of impact force during the same period of time as the heavier one because it has a lower momentum to produce the force and less energy to sustain it. Think of momentum as the torque a truck can produce and the kinetic energy as the amount of gas in the tank. In other words the heavier arrow has more "torque" and "gas".
4. The result is the lighter arrow does not penetrate as deeply as the heavier one.
5. Since flight through the air is literally penetration of air the lighter arrow runs out of steam before the heavier one simply because it starts with less.

In your example it doesn't happen more quickly. It simply happens sooner. The key here in this example is both arrows are being launched at the same speed.

Edited by Leo, 14 October 2010 - 12:42 PM.

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#11 Jeremiah

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Posted 14 October 2010 - 12:44 PM

Thanks guys. I really value your input. I tend to try and simplify things but doesn't this make sense or am I seeing things wrong?

Ok, lets take two identical arrows. Both 28". Cut one down to 20". Add identical broadheads to both. Doesn't it seem that the shorter arrow would then be lighter than the longer one? That being so, if both were fired at the same velocity, wouldn't it seem logical that the shorter arrow would lose energy faster? Of course that can be over come by adding a heavier broadhead to the shorter shaft but it still shows the length of shaft does make a differance.


Sure, that's true. But, that's not very common with most modern arrows and bolts. As I mentioned earlier, the 29" carbon arrows I was shooting from my compound weighed the same as my 20" carbon bolts for my crossbow. It seems as though most modern crossbow bolts are purposely made with thicker walls and heavier (sometimes brass) inserts to purposely get the weight back up to what it would have been if it were ~10" longer.

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#12 Spirithawk

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Posted 14 October 2010 - 01:18 PM

Sure, that's true. But, that's not very common with most modern arrows and bolts. As I mentioned earlier, the 29" carbon arrows I was shooting from my compound weighed the same as my 20" carbon bolts for my crossbow. It seems as though most modern crossbow bolts are purposely made with thicker walls and heavier (sometimes brass) inserts to purposely get the weight back up to what it would have been if it were ~10" longer.


Thanks again Jerimiah. The whole discussion is about these newer super high speed crossbows and being able to make 70 + yard shots with them. I just don't see it as a good thing to even try. Just too many things can happen in the time it takes an arrow to travel that far that could cause the shot to go wrong and I have to question just how reliable the accuracy would be at those ranges. I know guys with vertical bows make those shots but I still think it's as much luck as skill and not being fair to the game your hunting because of the greater risk of only wounding the animal. From personal experience, I think shots like that are even more risky with a crossbow than a vertical bow.

Edited by Spirithawk, 14 October 2010 - 01:29 PM.


#13 Jeremiah

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Posted 14 October 2010 - 01:38 PM

Thanks again Jerimiah. The whole discussion is about these newer super high speed crossbows and being able to make 70 + yard shots with them. I just don't see it as a good thing to even try. Just too many things can happen in the time it takes an arrow to travel that far that could cause the shot to go wrong and I have to question just how reliable the accuracy would be at those ranges. I know guys with vertical bows make those shots but I still think it's as much luck as skill and not being fair to the game your hunting because of the greater risk of only wounding the animal.


Big difference between shooting at long distances at stationary targets and live ones. I enjoy practicing/target shooting with archery equipment at ranges that are as far away as I can still see the given target with a naked eye. (Seems to be about 100 yards max.) But, I've hunted long enough to know that even if (by luck or blessing, for sure) most of the animals I commonly hunt do not react to the sound of the shot, the chances of them just simply taking a step (or 12!!! - at longer ranges) before the arrow/bolt arrives is just too great.

In my younger days, I'd take walking/running shots at white-tail with my rifle. I developed the ability to "lead" them fairly well. It always surprised me just how much I would have to "hold off" in order to hit them where I wanted/needed to even when they weren't out there more than 100 yards, or so. Well, we're talking about a bullet moving in quadruple digits of feet per second there. Here, we're talking about 350 to 400 feet per second in projectile speeds at the absolute maximum end of the scale. (It's really almost laughable by comparison.) I've never shot at a game animal farther than 40 yards away with archery equipment, personally. (I can see it being necessary to do more out west, for example. But, it seems to me - with my limited experience there - that elk, for example, are much larger targets than white-tail and generally don't have the same "instant" duck or bolt to them at the shot that white-tail do. They also seem to almost stop and stare out of curiosity more readily than white-tail which offers better shot opportunities many times. So, we're really talking apples and oranges there.)

I see it all the time though. There's always that one guy who just doesn't get it at each bowhunter ed. class. Because they can consistently hit a target at a given range they just automatically equate that to consistently taking game at those same distances. Well, a few gut shots (or outright misses) tends to humble many hunters. For the rest, it's probably just their nature to not learn from experience. (And if they don't even learn from that then you have just about zero chance of them learning anything by talking to them.)

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#14 PA RIDGE RUNNER

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Posted 14 October 2010 - 06:14 PM

I recall my first year of bow hunting about 1957. There were only a couple of us that ventured into bow hunting and there was no one we knew that had ever done it. We just read some books and tried what the book said. I know that first year I took a couple of shots at a much longer distance than I ever should have. Of course I never hit any of those shots but after finding a couple of folks that were very good shooters and hunters with a bow I saw the error of my ways in taking long shots. About the longest shot I took with a bow that I got the deer was about 40 yds and would not even try that today. Other than that deer all my hits came at 30 yds or less most times much less.
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#15 Spirithawk

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Posted 14 October 2010 - 08:52 PM

Thanks for understanding where I'm coming from. You know? One thing I can always count on from you all is that, even if you don't agree with a point, you at least try to understand it and back your own opinions with logic, common sense and facts. That's more than I can say for a lot of other hunting forums. The main question was, "Is there a need for higher speed crossbows?" One of the reasons a few wanted them is that they think they can take longer shots with one. The way I look at it, if a guy wants a super high speed crossbow, and they're talking bows like the Tac 15, then more power to them if they're willing to shell out the big bucks. But thinking that will give them rifle type distances that they can shoot at deer is just plain ridiculous. But when they actually go out and try it then it quickly goes from ridiculous thinking to unethical hunting in my opinion. Another point I was trying to make with them, these are a few guys on a crossbow forum, many of which complain about states not allowing them during archery season, is that a lot of states already look at crossbows as firearms. Missouri is one of them. Anyone that doesn't think so, I'd sure like to have exsplain to me why such states religate them to firearms season only, unless disabled with a permit. I know for a fact that the string being held in a drawn position is not the only reason alone. They've used the excuse of high speed crossbows as well. Making them crazy fast sure isn't going to change their minds any. Also, a deer killed at an ethical range does not know nor care the speed of the bow that killed it. One killed by my 316fps bow, which I think is more than plenty fast, is just as dead as one killed by a bow that has speeds of 400+ fps. Anyways, I'm glad I can count on you guys to be a voice of reason. That's one of the many things that makes this site so special.

Edited by Spirithawk, 14 October 2010 - 08:54 PM.





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