I think there has been a little confusion here, possibly due to a difference in terms. What SG500 has is not a Davy Crockett projectile, it is a 20mm subcaliber projectile. I believe that his concern is related to the fact that there were numerous types of projectiles loaded for the 20mm subcal (there was a 37mm as well), at least one of which contained DU.
The projectile for the Davy Crockett itself (nuclear) was an over-caliber projectile, fired from a 155mm or 250mm recoiless rifle. This is what is referred to by Hazord. His data is correct (though I might disagree with some of the yield figures) and it was a very basic type of implosion weapon.
There has always been a lot of interest on the DC 20mm sub-cal, and lots has been published in the IAA. If you cannot find any data let me know, I think I have some of it buried around here someplace.....
I do know that there were dummy, drill, and practice subcals. I have a couple myself, I can look for the photos once I get to work.