This is a slight side topic, but informative nonetheless. I know the conventional wisdom is that a 16" barrel will be faster than a longer in .22, but that may not always be the case.
I recently chronographed some .22's and the results were interesting to say the least. The two relevant firearms were a Marlin 880 with a 22" barrel and an old Sears pump action rifle with the barrel cut to 16.5". Velocities are the average of 10 rounds, with the chrono position ~10 ft. from the muzzle. The two loads were the Federal 36 gr. bulk pack load from Wal-mart, Winchester T22 and Winchester Wildcat 40 gr. The Federal velocities were 1247 (53 e.s.) and 1215 (76 e.s.) for the Marlin and Sears respectively, the T22 were 1209 (86 e.s.) and 1162 (121 e.s.), and the Wildcat were 1168 (81 e.s.) and 1170 (63 e.s.). So the Marlin was 35 fps faster with the Federal and 47 fps faster with the T22 but 2 fps slower with the Wildcat. Certainly not conclusive, but enough to pique my interest to do extensive additional testing. When I get the chance it'll be 50 round strings with these and other loads, but I don't know when I'll have the time in the near future.
Additional factors may be Marlin's Microgroove rifling vs. the more standard in the Sears. But 2 out of 3 loads is starting to say something against the conventional wisdom.
The other surprise was the high extreme spread on the T22. For a "target" round, even a budget one, this is rather surprising. It had a higher e.s. than the Indian surplus .308 which is generally considered to be absolute junk!
