Okay...having acquired a new M&P15 OR I need to get some backup sights. I have been considering getting some MBUS. Now, my problem is that I don't have a fixed front sight, I have a picitiny on the gas block which I'd like to put the sight on. I have heard and read that due to it being poly that it will melt with an kind of high continuous round count. I don't ever plan on putting four 30 round mags through it all at one time. I would like to get some tactical training with it at some point but even then I wouldn't expect that would cause it to melt. I do plan on changing out the hand guard to probably a MOE at some point so if that lends itself to a solution, do tell. SO....I'm hoping that those that have experience or friend/coworkers with experience w/ MBUS sights on gas blocks possibly would give me some feedback. Flat fish, Walther, Parks, Midget, etc., all opinions welcomed. Thanks!