I have a 22 with the Lonewolf 9mm conversion barrel. I like it. It's a match grade barrel and can supposedly eat any type of ammo. I've been firing 115gr FMJ and 125gr HP without any issues. Accuracy is great. Other than the barrel you need g17 mags. everything else functions as normal. And the key is: none of it is a permanent mod. Conversion takes about 20 seconds. .40 s&w around me is $18.99 on sale vs. 9mm at $10-13. For home defense I prefer a heavier bullet but for range I'd go with the smaller.