I just got a p22 as my first handgun... Kinda nervous now after reading some of your posts!!!
Hope mine lasts
I think if you stick with a standard velocity ammo - something around 1000 to 1100 fps (those ratings are clocked for a rifle barrel, but go with what it says on the box) the gun will last a long, long time. I had the dumb idea of using a lot of high and hyper velocity ammo... and the result was a gun that didn't last. I was shooting mine a TON and that didn't help either, I would suspect.
If you look at the CCI webpage it has good breakdowns on their products:
http://www.cci-ammunition.com/ballistics/rimfire.aspx
CCI Standard Velocity is a 40 grain bullet going 1070 fps (from a rifle) at the muzzle. With a 4-5 inch barrel it will be going sub-1000 fps. Green Tag is basically a more expensive version of the same thing (3 times as much IIRC). Supposedly it is more accurate, but you will need a target (competition-type) gun to really see the difference.
I used a lot of Stinger ammo, cuz it was really fun to shoot. It has a huge muzzle flash and it feels almost like a small centrefire handgun with Stingers. It's sort of the +P+ of the rimfire world.
Stinger is a 32 gr. bullet going a whopping 1640 fps at the muzzle. That is like 60% more velocity (although lower bullet weight). The "Segmented Hollow Point" is the same ballistics, its just a different bullet. Both use the longer casing. The Stinger has the silver looking case. SHP looks brass.
Velocitor is a 40 grain going 1435 at the muzzle.
Mini-Mag is a 40 grain going 1235 at the muzzle.
Mini-Mag HP is a 36 grain going 1260.
If personally would not go beyond the Mini-Mag type ammo with the P22 if I had one again. Actually, I would stick with Standard Velocity and enjoy my P22 for years to come. They are fun guns, but they are not built like a centrefire SIG, GLOCK, etc. Not at all. They will not take a serious pounding for very long. I was the big booster of the the P22 on this board for a long time. I was talking about how mine was "going as strong as ever". Then it started to have that issue where the slide wouldn't lock the hammer all the way back consistently, then it blew up when my friends wife was shooting it. That was it for me and the P22. I had my fill.