Rimfire ammo with powder tends to be relatively dirty in semi autos and handguns. Bolts actions run cleanest. That was a good point about varying velocity of loads advertised as subsonic though. The loads I listed ride the line and vary depending on ambient temps. Not much though.
Re: air rifles. I have seen some impressive air rifles, but the common stuff doesn't touch a rimfire for killing. Sq. are harder to kill than they get credit for sometimes. You can't always get a line on a head shot. I had to shoot a buck sq. three times a couple of mornings ago. Ambient temp. was in the twenties. Two to the chest brought it down, but still alive. Both shots were in the vitals, not entirely misses. You can quickly kill anything small enough, up to the size of a fox, by stepping on it to collapse the chest so it can't breathe. Nope, had to spend another dime shooting it in the head. And don't underestimate how far it is to the top of some of our bigger trees in GA. A sq. can get higher than you can reach with a pellet rifle or .410. Lots of us learned that as boys.
I wear ear pro for the high velocity stuff I run in my trainer carbine and revolver. The subsonic stuff from a 20" barrel isn't that loud. My cur trying to blow the top out of the tree is louder. 22lr is fastest from around a 16" barrel. The need for ear pro will vary, I guess. This begs the question of why would I want subsonic HP if I have a dog barking loudly. Subsonic HPs are more accurate and hit harder than high velocity stuff. You can hear the loud WHOP! High velocity isn't as accurate and doesn't do as much. Hyper velocity is different, but is seldom as accurate. I believe people have special chambers cut for specific hyper rounds to try to tame them. That's why the .17 HM2 exists. The hyper 22lr is a problem for accuracy. If your sq. aren't tame enough to easily slip within 30 yards, .17.
And, you may be surprised to find that those sq. that were driving you nuts in November have pulled a disappearing act after deer season. They're still there, but they are inside the trees replacing themselves. GA sq. are rutting now. After the next few weeks they will be scarce until the end of February. They stay inside and might touch the ground twice a day to get a drink of water and feed on stored acorns. I'm hardcore, taking the dog out a few times per week starting in late November or before. I give it up mid January and switch to trying to kill every coon on the hunt club.
There is great value in having a 22lr clone of your centerfire rifle as a trainer. And learning to tell the difference between a deer and a sq. and which kinda bird is making that noise over there. Ha!
