I don’t think that they expect to find fingerprints in the slug. It is far more likely that they hope to identify the model of firearm and to find peculiarities that might be used to match the bullet to the specific gun that might have fired it. That would be useful both to point them towards suspects and to serve as evidence.
Probably generic, but the design looks to me like it is inspired in the Sig Sauer P226 family.
If I had to guess, it is probably a P229 of either .357 or .40 caliber, because I don’t think that someone who wanted to kill Tracy that way would rely on 9mm ammo. The pistol and the caliber may well be clues; they are fairly typical of USA police and military.
I don’t think that they expect to find fingerprints in the slug. It is far more likely that they hope to identify the model of firearm and to find peculiarities that might be used to match the bullet to the specific gun that might have fired it. That would be useful both to point them towards suspects and to serve as evidence.