From what I've read the M855 and M193 aren't great against things that aren't metal or sheetrock.
I was thinking having something that penetrated light barriers (sheet metal, brick, auto glass, etc.) might be helpful in certain scenarios. Though its unlikely to ever have to use them, much less have the time to switch mags to the barrier blind ammo, its still something I'd like to have just in case. I could also use them for deer hunting I believe.
I've read the Barnes TSX will mushroom if it hits a soft target, but that if it hits something hard like glass it will shed the petals and its base will punch through like a wadcutter.
What I don't know is if the TSX is best (or at least very good (for .223/5.56)) at penetrating intermediate barriers, or if something like Federal T556TNB1 would be better.
Also, of the three different weights of TSX (55, 62, and 70 grain) which one is best for penetrating barriers.
Finally, since copper is relatively less dense than lead, if the 70gr. projectile will feed in an AR15.