What made it boring?
I have never experienced FA rimfire and to me seems like it would be fun.
Here's a quick list why full auto 22 sucks
1. It's dirty and your gun gets filthy and has to be cleaned every few hundred rounds
2. It's unreliable. I can shoot 9mm in my Uzi all day without cleaning and it will never fail. The BEST 22 conversion or gun will suffer a failure within 500 rounds. This is wholly attributable to the variance in 22 ammo both in its sizing and its powder load.
3. It's expensive regarding ammo. Although we think of 22 as cheap, the cheapest 22 ammo is the worst to run. Decent ammo like CCI Minimags are about 100 per 1000. Right now you can get 100 rounds of Tul 9mm for 140. I can typically reload 9mm for an amount somewhere in between those numbers so the cost savings for 22 is negligible.
4. It's expensive regarding guns. Arguably the best 22 transferable is the Norrell 10/22 conversion. They are currently around 20k. The second, the American 180, is around 15k. An Uzi 22 conversion is 675 and a M11/9 conversion is around $600 I believe. Of course with each of those you would need more magazines etc. That's a lot of money spent to save pennies on ammunition cost.
5. It's boring. Sure you will giggle a couple times after shooting a mag of 22 in full auto suppressed. After that, it will feel like a stupid pellet gun. Personally, I like a little recoil with my shooting.
6. It's too fast. All the 22 fullauto guns and conversions run fast. We are talking like 1,100 - 1,300 rpm fast. Even BWE's slowfire conversion for the Uzi only gets it down to like 975.
My recommendation is to don't be an idiot like me. Don't spend a bunch of money for 22 conversions that are unreliable and boring. Use those savings to buy more correct ammo for your gun and spend a little extra to get yourself full auto bb gun. I guarantee that BB gun will be just as fun and more reliable than a 22 conversion.