Easy to set off .22 rimfire?

I'm having some trouble with two .22 rimfire pistols, with most ammo I try in them.  The pistols are a 1948 S&W K22 and a Walther GSP.  Ammo I have had trouble with includes Aguila Pistol Match, German-made Wolf Match Target, and CCI SV.  

Is there any accurate .22 rimfire ammo out there that is acknowledged as the easiest to set off?

When was the last time these guns were cleaned - especially chambers?
How old is your ammo?  Never had problems with Wolf or CCI, never tried APM
How often are the failures?
Do you have pics of the firing pin strikes?
Do the rounds fire if you try them a second time?
- Dave

My 6 22's all tell me when it is time to clean them by giving me misfires.

Allen Barnett wrote:My 6 22's all tell me when it is time to clean them by giving me misfires.

Yep, and if one of them is a Benelli, that chamber cleaning is about every 20 rounds!  

To the OP, Dirt / carbon / lube / whatever, builds up in a tight match chamber quickly. A cartridge may not get fully chambered by the slide / bolt. Then when the firing pin hits, it pushes the cartridge forward that last few thousandths of an inch, leaves a dent on the rim, but not enough of a dent to ignite the priming compound.  I never had this problem until I bought a Benelli, but never had a real match grade pistol until then. I've gotten into the habit of brushing the chamber out after every 10 shot string with a 6mm bronze brush. Last month I shot in a .22 only 2700 match and made all 270 shots without an alibi, not one. Before the brushing routine, at around 50-60 shots it was nothing but troubles.

The K22 could just have a weak spring. It is 61 years old. It might be time to change it.

Len   They are not expensive.      www.midwayusa.com/product/365183/wilson-combat-custom-tune-spring-kit-s-and-w-k-l-n-frame

I agree with Len.

Also, make sure the strain screw is fully tightened.

Don't go too light on the mainspring. The .22 revolvers need more whack on the primer than the centerfires.