i tried to get my G2 contender on paper with the green stuff once. the first round extracted fine, second was a little sticky, then the third was frozen in there and when i opened the gun the extracter snapped off. it was a brand new gun never fired before. i took it down to specitaly sports and lawrence got the shell out. it took him 15 min and a lot of hammering. i had to send the gun in to get the extractor replaced. lawrence said he has to do that to an AR a few times a month. i'm not sure if they grey stuff is better than the green but i'm not taking a chane with it. i save it for my AK. i think i can recall someone on this site getting the green stuff stuck in there AR a while back as well.