A question so strange it requires explanation

Greetings to all and sundry! I joined this forum specifically to ask this question, but I realize that it is so strange I had best explain myself first.
I got into adult air rifles two years ago after an impulsively bought Savage .17 HMR (A beautiful instrument, but alas) languished on my gun rack, only offloading ten cartridges and eventually being sold. Living in city limits, it was not legal to use for the plague of rabbits that bedevil my garden and stock my freezer.
I started with (I still groan to think) a Gamo Silent Cat, bought from Walmart. I still have it and use it (and like it, heretical though that sentence is), but I wanted something... more serious. So, I got a Hatsan 155 Torpedo Vortex (an underlever gas-ram with walnut stock). Now, both have been broken in and I love them both, but the Hatsan presented a new challenge, ammunition-wise. I should also mention that both are .177's. Until the local raccoon population started to get aggressive, buying .22 pellets didn't appeal to me when I could use the same pellets in both guns.
The Gamo did fine with easily available off-the-shelf pellets (Crosman Gold Flights being its favorites), but the Hatsan is so powerful it flings anything less than 10 grains supersonic, killing its wonderful accuracy. Crosman Ultra-Mags and H&N Sniper Magnums do well in it, although I prefer the ranged flight characteristics of cylindrical pellets like the SM's. It still fires them around 1025 FPS, generally excellent for rabbits. I've looked at H&N Rabbit Magnums and Piledriver pellets, but the price and mixed reviews make me leery of a blind buy. Even though they are generally remarked "PCP only" (and I have no interest in PCP rifles at this time), I'm very confident the Hatsan could squirt them out with authority. However, an unrelated trip to my local sporting goods superstore planted the germ of an idea in my head.
If you have read this long-winded explanation, my question is simple- Has anyone ever tried firing rifle bullets (the kind they sell for reloading) through a magnum air rifle? Just looking for a few more joules at impact for those thieving raccoons. .17 bullets with a true diameter of .172 might be a little small for a .177 (though the Hatsan's breech is quite snug with most pellets), but what about a .22? I have a .22 Hatsan 135 on the way, and I am curious before I start experimenting. Thank you for your time and patience with this befuddled neophyte.
 
With few exceptions, the bores of firearms and airguns are slightly different. However, they are different enough that it will be difficult to find bullets that fit. For any reasonable accuracy, the bullets must fit the groove diameter of the barrel. (Certain cast bullet designs need to fit both land and grooves.) 

Jacketed bullets will not be useable in an airgun for you won't have the ability to get them started in the rifling. Finding soft lead cast bullets is also going to be a near impossible task for the smaller .177 and .22 calibers. 

But, the good news is that there are bullet molds now being made for airgun use. NOE is but one maker that is starting to stock some, and have choices on diameters of the bore (land riding portion) and the driving band (groove riding portion). Thus, with the right alloy of lead and tin, you can get a bullet to fit. 

There are a few who have shot cast bullets of this sort in PCPs, but I am not aware of anyone doing it well with a spring gun---yet. 
 
This isn't strictly an answer to your question, but I'd recommend that you try the JSB Exact Beast Diablo pellets in your Hatsan. The pellets are darn near slugs, but they do have a skirt, a mini-skirt if your will, unlike the H&N Rabbit Magnums. That means that the JSB Beast Diablo's will be easier to push through the barrel, but they weigh so much that they slow down the velocity and increase the fpe that they hit with. The lower velocity might preserve your accuracy while increasing the energy delivered to the critters. At 16.2gr they're actually heavier than some .22cal pellets.

http://www.pyramydair.com/s/p/JSB_Exact_Beast_Diabolo_177_Cal_Pellets_16_20_Grains_Domed_250ct/1197



for comparisons sake, here's a standard JSB pellet compared to the Beast Diablo:
 
I second the use of the JSB Beast Diablo 177 for the conditions and critters you are after in the springer. I use them, they work, they slow down your velocity, they are accurate both through a cheaper Gamo Whisper and shoot really well from the RWS 350 Magnum. By a small tin and try them out. If they are accurate in your rifle then use them. By far the additional foot pounds of energy from this heavy pellet will do the work for you without question.