Energy needed for a reliable kill on small-med. game?

well if you look to the brits nothing is more than 12 lbs and they do a great job at dispatching vermon ,,,i no its not the answer u want ,,like u said shot placement is the key,,, pat 

This is a topic that comes up regularly on here. I would try the search option. In my opinion the most important issue in shooting any critter is accuracy. My old .20 cal sheridan pumper has put down more rabbits, squirrels and birds than I can remember. Maybe 12 ft lbs at the muzzle but very accurate. If i could only have one gun and was lost in the woods that is what i would want. 

I was thinking along the same lines didn't want to setup the chronograph wanted a method to ensure good speed
I would set up a Sears Christmas 500 page catalog with a good metal back stop, just in case, at about 12 to 15 feet indoors and shot it
I noticed every gun that was over 600 fps would go about half way through (I'm counting all damaged pages).
I found that if i went point blank with the book on the floor flat i would get different results
my modded disco would penetrate only a few pages but the pellet would be flat as a pancake probable having the do with the it lying on the floor.
I haven't tried anything other of my air rifles with that method but i thought it was note worthy. 

I just use water jugs and bottles in a straight line to compare pellets. One pellet may go thru 2. Another thru 5. Ect. 

Concerning hard mediums, I just pick something that I know is a lot harder or denser than my intended prey animal and then simply try it. If my pellet can penetrate my practice item that is harder than my prey, then I know it will penetrate my prey.

For instance, my .30s can penetrate thru 3/4" pine or a 1 gallon jug of water at 100 yards at 74fpe. I figure 3/4" pine is a denser target than an average hog skull and 1 gallon jug is more dense than coyote lungs. So out to 100 yards, I have confidence the .30 pellet at 74fpe can penetrate either area on those two prey animals. 

And then I actually go out and do it on a living animal to test it. To date, real-world penetration in even large animals has always been deeper than my practice mediums. 

As far as an FPE rule, I now disregard energy deposited into an animal and instead focusing on the wound channel created, with FPE only relevant to ensuring deep penetration for said wound channel. I think of air gun projectiles as being arrows w/broadheads simply in another form. I want enough energy to penetrate deeply or clean thru the other side and I want a big enough hole to disable the brain or the lungs, with the knowledge that it takes a much larger hole to disable lungs than it does a brain. 

I found a somewhat fair list, not by any means exaustive, started a topic on it: http://www.airgunnation.com/topic/impact-energy-requirements-for-hunting-various-animals-2/

I go by field experience, never had a block of ballistic jelly or a magazine run out in front of me in the woods. That said I do know my .25 will put medium game down out to 75 yards with a head/neck shot. That's woodchucks, Racooon and possums. The .22 will do the same out to a good 40 yards. My .177 MRods have taken several woodchucks out to 50 yards but that was threading the shot into ear every time. I use 35 gr JSB mark2 in .25, 18.1 JSB in .22 and Crossman premier 10.5 in .177. All my guns shoot around 900 fps to keep bark down. The larger the caliber the more forgiving the shot can be. Just what I have used and seen in past several years of PCPs and break barrels. 

yes they are lethal. 

I use marbles from Dollar store, cheap and provide a lot of blunt force trauma. Get a whole bag for a buck and easier to hold than bearings. 

@ Hookster, nice HTS and great shot!! I have mine setup the same way with the double theraband. Mr. Hays makes some great stuff!

My personal experience with a .22 Diana 34 ( had it a while, conograghed at 650 fps) and 14 gr. crosman pellets. Bunnies, squirrels, doves, ferrel cats, good to 30 yards, head, heart, lung shots. Raccoons, 30 ft. max. It was in the trees at nite wearing a head lamp, aiming at eye reflections for head shots, iron sites. Raccoons were trying to invade our attic for winter nesting. I finally removed a tree after the wife went to visit her daughter for a few days. Life was hard for a few weeks, She sure missed that tree and then she realized it gave the raccoons access to the roof.