Weapons grade is kind of a nebulous term. In the broadest sense it means anything isotopically pure enough to make a working bomb, and in that sense Little Boy obviously qualifies. However, standard enrichment for later uranium bombs is typically around 90%, and according to Wikipedia, Little Boy was around 80% average enrichment.
It is well known that once you have weapons-grade fissile material, building a crude bomb requires little more than a machine shop. Isotopic enrichment is historically slow and expensive (and hard to hide), but there could certainly be tricks not yet widely known…
Weapons grade is kind of a nebulous term. In the broadest sense it means anything isotopically pure enough to make a working bomb, and in that sense Little Boy obviously qualifies. However, standard enrichment for later uranium bombs is typically around 90%, and according to Wikipedia, Little Boy was around 80% average enrichment.
It is well known that once you have weapons-grade fissile material, building a crude bomb requires little more than a machine shop. Isotopic enrichment is historically slow and expensive (and hard to hide), but there could certainly be tricks not yet widely known…