Firstly, congrats on this shell, I never even heard of them. I thought SALVO was about multi-projectile rounds.
Secondly, after investigating SALVO, I found the following “In SALVO testing they were found to be able to penetrate one side of a standard steel helmet at 500 yards (460 m)—excellent given their light weight—but the dispersion of the darts was so great as to make them only marginally useful” (Wikipedia). I could have guessed this without being a ballistics expert.
Thirdly, if there is no wad, what keeps flechettes from falling out?