L.C. brass is not lower capacity than other .223/5.56 brass.
This myth regarding military 5.56 brass is due to some military 7.62 brass having less capacity.
From Sierra Bullets, Loading for Semi-Autos and Service Rifles:
link "While this is most often the situation with both 308 Winchester and 30-06 cases, it is less true with the 223 brass. We have found that military cases often have significantly more capacity than several brands of commercial brass. Again, take the time to do a side-by-side comparison of the cases you are working with and adjust your load as needed. There may be no need for such a reduction with the 223. Know your components and keep them segregated accordingly."
I have measured the water capacity of most common brands of .223/5.56 brass and IMI, CBC, LC, and Remington had the highest capacity. Winchester was among those with the lowest capacity.
This myth needs to die.