the second build is officially on 28 inch ELR build

[tdbru]

though my thoughts are only worth exactly what you paid for them, i think the low mass bolt carriers only work well with an adjustable gas block. i think you want the chamber pressure to drop low enough for the brass to contract off of the chamber walls before you try and extract the case. With a low mass BCG, all else being equal, for the same gas volume & pressure, that extract cycle will start sooner. If too soon this might cause extractor failures, will likely be quite hard on the rims of your cases, and if you don't reload them, then you don't care how bad the cases get beat up I suppose. Also the BCG will have a lot faster cycle rate, unless you tune the gas down or change the buffer mass or other such things, and may be outside the design envelope for BCG cycle speed and may have the bolt going into battery before the round in the magazine get's pushed up to the feed lips of the magazine and your BCG fails to strip a round off the magazine because of too fast a cycle speed.

i think the low mass carriers were a request by the guys shooting the speed matches where fractions of a second in cycling might make a difference on the outcome of a match.

for normal use, I don't see a need for a low mass BCG, but if you have a tuneable gas system and want to give it a try, I don't see that it is a big deal either.

i would proffer that the $ would be better spent, particularly since you already have some bcg's, on more ammo or reloading components for more practice or more hunting. just my opinion though.
-tdbru