Like what the bodger says, just to highlight how ineffiecent .177 is, I replaced the 16" .177 barrel from one of my Rapids that was set at 11.7fte and swapped it for a 19" .25 ( everything except the probe remained the same) I was obviously expecting a power hike due to cal and length of barrel but was shocked when I checked it on the chrono, it was in excess of 21fte, nearly twice the power for the same air consumption. Another test without changing anything other than the barrel, I replaced the 16" .177 for a .177 barrel only 95mm long, it produced 7.5fte but was really loud.

Despite its ineffiecency, I still love the .177.