.22" is likely better in terms of dumping energy into the critter without over-penetration and pass-through. That is if you're talking about sub-500fps air rifles. A .22" at 490fps with an RWS Hobby 11.9gr pellet is sub-PAL, and delivers approximately 5fpe at 60 feet. A .177" pellet weighing 7gr and travelling 490fps delivers only about 3fpe at the target range you specify. I'm going by about a 1/4 loss of energy from the muzzle energies of 6.35fpe and 3.73fpe for the above pellets respectively. With a well placed hit, 5fpe should be enough. 3fpe is unlikely to do the job humanely. If you're going to PAL-rated velocities then it comes down more to blast noise in your circumstances. Still, a .22" is more efficient and likely quieter at any given power level. A 20fpe .22" is likely quieter than a 20fpe .177" with similar power plants, as the 177" has to push a lot faster to achieve the same energy level. If I were picking a sub-500fps rifle for this Jo I'd go with a nitro piston .22" and use JSB Exact Express 13.43gr pellets. Closest I have to that is a QB57 in .22". It's quiet and quite accurate.






















































