Help me max out my crosman 2250b

This ones for all the 22XX owners out there:

hey guys. I’ve just bought myself a crosman 2250b ratcatcher and I’m planning on tuning it up for pest control on my farm, primarily rabbit and possum. I’ve had years of experience shooting with break barrels (higher fpe than the 2250 though..). I’ve read a lot of mixed information regarding wether or not the 2250 is suitable for this sized game so I intend to find out for myself.. The incentive to use a co2 airgun (and adding multi shot breach) is definitely a big one for me as it’s a bloody nightmare trying reload a break barrel in the dark, knee deep in cow poop ;) .. there are other higher powered co2 Airguns floating around but they’re a little bit hard to get hold of down here. I also like the idea of tinkering around with it for a hobby. So now you know my incentive to use such style Airguns my questions are: 

-1) what is your dream set up for max power on a 2250 running co2?
-2) if money weren’t a limiting factor, what mods would you do to achieve max power? 
-3) first hand accounts? If so what’d you do? What kind of power did you get? 

I reiterate, no PCP or HPA.. 

The reason I cannot go PCP or HPA is because they require a licence where I live, however there is no limit on FPE like they have in the uk and other places. 

Lastly i know there is no substitute for a well placed shot.. I've dropped many bucks with a low powered air rifle, but I’d still love to have some extra ooomph on my side. 

CHEERS GUYS!

 
"shambozzie"Try Mountain air custom air guns. Roy can supply you with custom high performance parts (valve) or complete gun. Very knowledgeable and nice guy to work with.
Cheers mate! I just had a look on their website. I noticed they’ve got a .25 cal converted 2250b which is very interesting. Definitely something to consider. Nice one shambozzie. 
 
The first you will want to do is valve work, or buy an upgraded. if you have a dremel/rotory tool and a drill press you can do all the mods yourself. 45 degree port, and the valve stem can be worked in the drill press. most remove a few threads from the valve body to increase valve volume. Replacing the internal spring with a lighter one will allow the valve to stay open longer. you can you tube that stuff. Replace the stock transfer port. You could open up the stock one. Its a pain. You can get a custom one, or replace with 1/4 vinyl tubing.
The hammer spring can be replaced with a heavier one. After market adjusters are available, but not as inexspinsive as simply useing a heavier spring.Polish the hammer tube to reduce drag.
You said you will add a multi shot breach. There may be room for improvement of the bolt. Again you could modify the exsisting by turning down the bolt so its diameter is that of the inner diameter of the pellet skirt. Ive done so with a drill press and a file. 
Finally a 24 inch barrel will ad more accuracy, but I have read in a few places a 20" seems to be the best legnth
Then there are trigger group mods, but that dosnt effect power