this is the third time I have tried to post this. there are some versions of the S&W M&P15 that do not have dust covers, in fact they have no provisions for a dust cover. They are called S&W M&P15 Sports. One of the reason they are an affordable rifle is that they left off some of the normal things that were put on as bandaids.
I happen to own one. In the last 6 months it as made more transformations than you would imagine while I searched for its roll in my world. To make a long story short, the rifle did more than I can ever expect...If you are headed with that particular rifle, to the sandbox, I might be a little concerned but I am not sure, knowing good soldiers I am not sure but the rifle wouldnt be wiped out and functioning fine