The only thing that will screw up the firing pin is firing the gun, which if you use the BMF activator you are going to be doing a heck of a lot more of.
I've see a few full auto .22s in my life. Coolest ones are the Tippmans.... scale mock-downs of WW1/2 machine guns. They made a 1917 watercooled and a 1919 both in .22 LR.... belt fed... had a canvas belt that you fed the cases through. Not very accurate, but for a full auto gun its pretty cheap to shoot! They also did a Browning M2 scaled down and chambered in .22 Mag.
I got to shoot a 1919, had a mini ammo can, small violin type carrying case... very very cool. Damn things are very expensive though....
Heck I even found a picture of one:
Tippman 1919 .22 LR Machine Gun
Here is one that is similar... only in .17 HM2.... don't blink... this 5 second video clip has an ammo bill of about $10.......
17 Mach2 Mini Machine Gun
Click on the video-clip link to see the movie.