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I have often read in these forums that the generally accepted minimum amount of energy to harvest a deer is somewhere in the range of 1,000 foot pounds of energy.

What I haven't read is to effectively harvest a deer, what's the minimum required weight in grains/ounces of the projectile generating that 1,000#s' of energy?

Maybe this is more a question for those experienced in hunting with rifles where the bullet sizes are normally under 200 grains. Is that magic number is still 1,000#'s? If so, then what's the minimum grain factor....180gr, 150gr, 120gr?

I realize this is a shotgun forum and slugs/sabots are usually being discussed ranging from 260 gr (5/8 oz) in 20 ga. to 438 grains (1 oz) in 12 ga. And I guess I'm still a little hung up on at what range a 20 gauge is truly effective to. Shot placement being the same, is a 20 ga at 1700#, 1300# or 1,000#'s just as effective/deadly as a 12 ga at the same energy level or is there some point where the smaller size of the projectile enters into the equation? Knowing if that same 1,000# threshold applies to you rifle hunters using sub-200 gr. bullets would put my mind at ease!
 

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Kinetic energy = 1/2 mass x velocity^2

momentum = mass x velocity

these are the correct equations, someone else will have to apply them to your question.
 

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If you know bullet weight in grains and velocity in feet per second, you can calculate engery in ft-lbs. Multiply velocity times itself, then multiply that by bullet weight. Take that number and divide by 450,380. This gives you energy in ft-lbs.
 

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wow threads like this make my head spin cuz i got an NRA book after i finished my hunter safty class and i read a bit of it and theres countless formulas out there from everthing from figuring muzzle energy all the way to figuring felt recoil
 
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Energy of the projectile is not the sole determination of whether the bullet will harvest your deer. Diameter(caliber) velocity, shot placement and bullet construction all have a part in determining if the shot will harvest(kill) the animal. A heavy projectile in large caliber at a modest speed with a mostly non expanding bullet can knock down a deer with correct shot placement. If on the shoulder point, it will break both shoulders, blow out the heart. A high speed small (222 say) expanding bullet for deer can also break the on side shoulder, blow out the heart and kill the deer. So whether 1000 ft-lbs is magic number or not, the other factors need to be considered. A 1000 ft-lbs of energy in a light expanding varmint bullet may not down your deer but just blow a surface hole in the animal.
Shotgun slugs are generally limited by accuracy to about 100 yds or so. Whether 12 gauge or 20 gauge, you don't have to worry about energy, either will do the job. -Dick
 
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