Im not familiar with the rifle but whenever I have had a .22 semi auto that did this it meant there was buildup preventing the extractor from grabbing the case. On one rifle the carbon looked like it belonged. Wasnt till I poked it with a dental tool that I saw it wasnt right.
Keep in mind you need a different buffer. This http://www.brownells.com/rifle-parts/receiver-amp-action-parts/receivers/upper-receivers/9mm-entry-upper-receiver-kit-sku100010660-54610-105787.aspx shows all the parts required. Also the KNS anti rotation pins are a good idea http://www.brownells.com/manufacturers/KNS%20PRECISION%2c%20INCxzzx/index.htm
Brownells has a branded offering on and they are on sale. http://www.brownells.com/magazines/rifle-magazines/magazines/brownells-ar15-32rd-9mm-magazine-prod57092.aspx?ICID=8019&avs|Make_3=AR-15/M4&avs|Cartridge_1=APP_9%20mm%20Luger
Lastly you can buy Uzi magazines for next to nothing and modify them to work. Here's a pistol version http://forum.308ar.com/topic/5884-latest-creation-9mm-ar/
I used the Hahn top loading block http://www.brownells.com/rifle-parts/bolt-parts/caliber-conversion-kits/ar-15-9mm-conversion-block-prod1548.aspx Anyhow 32 rounds of suppressed goodness :thumb:
Anything Colt branded is pricey. These mags are supposed to be identical if not the same exact ones http://www.jsesurplus.com/ASC9MMSS32RdMagazine.aspx
Colt mags are the best, pricey but worth it. http://www.brownells.com/magazines/rifle-magazines/magazines/magazine-assembly-32-round-9mm-prod23233.aspx I have some from the company that supposedly makes them but have not tried them yet.
Im no stranger to the double stack 1911. I carried a Para P12 from release date until two years ago. May end up going back to it with 10 rounds though :( I like the modular approach of the STI but Caspian makes good stuff and I know they are good people.