My question is why do they make prop guns in the exact same caliber as real guns? Yes, I know prop guns can kill you with a blank but, if you made the prop gun slightly off caliber, you couldn't shove a 9mm, .38 or .45 in it when nobody was looking or by mistake.
I saw a documentary once about movie guns and in most cases with close ups they use real guns because they are cheaper and more readily available than copies that are close enough to be scrutinized. For action shots and drop the weapon type stuff they are rubber guns so not to damage the real guns. John Wayne only used his own personal guns in a lot of his westerns. There was more than one mistake made in this instance with Baldwin.