At the beginning of this year I built two LMT 16" M4 clones, out of defender 2000 lowers, and lmt 4 uppers, with identical operating systems. Carbine gas sys, lmt enhanced bolt carrier and chromed bolt, h2 buffer w/ hd action spring. Since I have changed all my brit sa80 mags over to wolf springs w/ magpul enhanced followers, I have elminated mag malfunctions altogether.
Both carbines have a nearly identical fit and finish. Frankly its not the most amazing finish I have ever seen, but aside from scratches I did, the finish is uniform and even, and of good dark/rich color.
The upper/lower fit is a not exactly loose, but it certainly isn't super tight either. It has a bit of play. Actually, its very close to the upper lower fit I have on almost all of my colt factory rifles. The front sight tower was dead nuts on both rifles.
Both of these rifles have been unstoppable so far. It took close to 2000 rds to stop the one I did an endurance test on. And even then I just needed a little forward assist action.
Others can form their own opinions, and im sure there are people out there differening experiences, but I have been impressed so far. I think they compare favorably with my Colts, and those are hands down my favorite.
Take care
John F.