What is the minimum fps you need to hunt deer with in a crossbow?

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Originally Posted by delmer

Speed alone is not a good indicator of a bows ability to harvest an animal. The question you should be asking is "how much kinetic energy do I need to humanely harvest a deer?" The general answer to that is something around 45 ft/lbs. Kinetic energy is a factor of the speed and weight of the arrow. The amount of KE produced is easily calculated using this formula;

KE = (arrow weight / 450240) x (velocity x velocity)

Usually the advertised fps rating is achieved using the lightest arrow recommended for the bow. For example, a bow that uses a minimum arrow weight of 350 grains achieving 305 fps would have

(350/450240) x (305x305) = 72.3 ft/lbs of kinetic energy

Simple, right?:D

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I'll complicate things even more and say that it's actually momentum that plays a greater role in determining the penetration potential of an archery setup.

" If one studies KE and momentum they would conclude that momentum formula results are more meaningful to the bowhunter as momentum can be translated into penetration potential."

http://www.tuffhead.com/education/fo..._momentum.html

From some experts...."According to Easton, a 400 grain arrow traveling at the glacial speed of 170 feet-per-second has sufficient energy to harvest a mature deer."

To kill a deer you need about; "25-41 ft. lbs."

http://bowsite.com/bowsite/features/...r/penetration/

The rest of the theories are marketing...

Quote:

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Originally Posted by delmer

Speed alone is not a good indicator of a bows ability to harvest an animal. The question you should be asking is "how much kinetic energy do I need to humanely harvest a deer?" The general answer to that is something around 45 ft/lbs. Kinetic energy is a factor of the speed and weight of the arrow. The amount of KE produced is easily calculated using this formula;

KE = (arrow weight / 450240) x (velocity x velocity)

Usually the advertised fps rating is achieved using the lightest arrow recommended for the bow. For example, a bow that uses a minimum arrow weight of 350 grains achieving 305 fps would have

(350/450240) x (305x305) = 72.3 ft/lbs of kinetic energy

Simple, right?:D

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Hell, the recommended foot-poundage to send an arrow clean through an elk is 52 ft-lbs.

You don't stop hunting because you grow old. You grow old because you stop hunting.
- Gun Nut

Just like Doug mentioned previously. Look at the regs for specs & minimums for bows/crossbows. That's your bare minimum.

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Originally Posted by MikePal

From some experts....
To kill a deer you need about; "25-41 ft. lbs."

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Well, I said around 45 ft/lbs, so 41 ft/lbs. falls within that area.

Thanks for the confirmation.:thumbup:

There is a great article in the OOD magazines latest issue (Nov/Dec) that explains this topic well in my opinion!

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Originally Posted by robster

Just like Doug mentioned previously. Look at the regs for specs & minimums for bows/crossbows. That's your bare minimum.

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Speed is not listed at all, just draw weight. Since arrows kill by cutting and not that is what causes the shock as long as the arrow penetrates enough to get into the lungs/heart area it does not matter how fast the arrow is traveling. I went to a much faster bow with a much heavier draw weight but it was not for energy it was to reduce the rainbow trajectory, my old 220fps bow vs my 350fps bow, a huge difference on deer size game out to 40 yards.

Fox, the draw weights (DW) speed (FPS) and energy (KE) are shown in the chart on page 25.

The article is a fairly good look at a few different bows to help you decide what you feel is important for your hunting needs.

edit add: re rainbow effect...I wonder what the arrow drop between 20-30 yrds is compared to the different speeds. I know with my old 150 lb x-bow it was insignificant and accommodated for with the ballistic reticle. Much more between 30-40, so I don't shot that range.

Found this article to help explain away some of the myths and untruths about speed and arrow drop....some excellent examples, with corresponding graphs, worthwhile reading.

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There are those folks who will claim that they hold dead on with their pin and any distance up to 40 yards and hit the center. This is blatantly false and these people are either telling tall tales or subconsciously holding high or low. I have had the personal pleasure of shooting some of these “magic” bows and holding dead on with the pin and watching the arrow hit high or low. It’s not possible to outrun gravity! Some of the bow’s owners will claim that I aimed lower or such, and they have surely deluded themselves into either trying to save face or completely believing their own defiance of gravity.

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http://archeryreport.com/2010/03/arr...-pin-40-yards/

My crossbow shoots about 275 fps and sends arrows through deer, in one side and out the other, diagonally.