[Unclenick]

NW Pilgrim hit it, I think. If you haven't resized them yet, the measurement is meaningless. After resizing them if they are still short, then they have either been trimmed more than usual by a previous reloader or they are a brand that is normally short. You occasionally run into that with specialty bullets, though I don't recall seeing it in .223, specifically.

The short cases won't likely give you a problem with long, heavy bullets. It used to be a standard service rifle match shooter's trick to cut cases for long match bullets down an extra .015"-0.020" below SAAMI minimum just so you didn't have to trim them again before you retired them. That's usually within five loadings for the M14/M1A using military brass. The same could be done with the .223 if you have a fast enough twist for the longer bullets.

The SAAMI spec for .223 cases is 1.740"—1.760". The standard trim length is simply in the middle of that range.