Built this to replace my M16 for a handy house gun . Got the gas system/piston depth adjusted to run SS109's @ about 8-9 hundred rpms. It'll run the weaker loads but the ejection is a bit weak , throws them about 4-5 ft. With the SS109's , it toss's them 12-15 everytime . Used a Saiga .223 rec. , a Bulgy 5.56 trunnion and barrel ,set it for Galil mags and used a Galil bolt and carreir . sights and forearm are HK .