A few years ago I built a 22 Mods for All 5.5" 9mm pistol using their upper. Got a good deal on a ProMag 9mm adapter and bought 4 of their 9mm plastic mags with the steel inserts. Ran it for about 100 rounds and the plastic lower I had cracked, but otherwise the unit ran well. OK bought an Anderson lower and transferred all parts but after finishing it the first time out broke the bolt hold open and the Pro Mag adapter. OK got parts under warranty, got info that the polymer lower would not hold up under the 9mm so that was why the Anderson lower. Got lots of advice on this forum and tried most of it but kept breaking parts, just enough to question reliability. Finally decided to get the Endo Mag inserts and assembled same. Got sick and all sat for quite a while. Then I got afraid to try it out not wanting to "break" it again. Finally got to the range today, ran all 3 Endo Mags without a hick-up. Guess the "I should'a listened" info was totally correct. I just wanted so bad to get the look of the 9mm mags but it's not worth it and by not listening to the advice given to have to go through all the problems. I have the 22 Mods For All 9mm bolt and the 5.5oz buffer. Normal springs and all else is normal including the Kak brace and flash can. Overall like the look and function at this time. Ran slightly over 120 rounds through the 3 Endo mags and only had 1 misfeed as I didn't fully seat the mag. Finally I think I can say I'm happy and can live with it.

(Jeff. by the way I also ran your adapter and it also ran well but again broke the finger off of it, hopefull you are still around and happen to read this.)

By the way sold the polymer lower, Pro Mag 9mm adapter and 4 mags and got $125 for all but that was before the current shortages. Might have gotten more if I'd waited but just wanted it gone.