i have a dpms sst lower (not a complete rifle yet) and i just got the new bm 10 rd mag and one of the 40 rd mags from their site. anyway the 10rd one fits a little tight but not to the point where i'm not going to use it. the 40 rd however, fits extrememly tight and i'm scared that if i put it in all the way it will get stuck. this happened before with a 30rd mag i got from a local store and when i brought it back it fit fine in an AR they had their but didn't fit in my lower....so question is-is it my lower or the mags? the 30rd thermold mags seem to fit in the easiest.