I converted my 2240 from the factory short barrel to a 22 inch .177.When it was around 75 to 80 degrees outside, it would push 7.9grain CPHP's to 710 fps.And it was very accurate.Ray
Once I put a heavier hammer spring in, a 24" .177 barrel, I could throw 10.5grain Ultra Mags at 675 or so. 700 on a hot day no problem. And it was dead nuts accurate too. Fun guns, but CO2 isn't for me. Not when the temperature here fluctuates 100* between summer and winter.
WHAT IS THE SWEET SPOT ? FOR ACCURACY .& VELOCITY .