anyone have any knowledge or experience with these? have looked everywhere,at every review and sales site. seems to be 1/7 barrel 8-16",5.56 chamber,short piston action. has been hard to get a firm take on twist rate and exactly which chamber it's cut for. however, they do seem to be 1/7 5.56. just wanting to know if anyone has hands on impressions or experience.have seen reports of probs with 7.62x39 guns. othr posts and reviews seem fine. thinking about getting one if i can confirm good news. tx for any input.