Or you can go with CCI CB Long (or short), 29 grain, 790 FPS = 40.2 FPE You can get a decent bolt action 22LR rifle for $150-$350. CCI CB Longs are about $8-9 per 100, so call it 8.5¢ per shot. Compare that to, say, an AA S410 new for around $1200, plus a scuba tank and fill adaptor, another $250, and .22 cal 18.1 JSB Jumbo Heavies at around $10 per 500 shooting at about 30-32 FPE. The thing to consider carefully about a 22LR, all else aside, is that you are shooting a firearm and different laws apply than for air rifles. But either a good PCP or a 22LR with the right sub-sonic ammo can be comparably quiet, and equally deadly to small rodents.