There is two different sizes in primers. Small and large. Then you have two catagories in that of regularand magnum.

45ACP, 44mag, 45 colt, etc all use large pistol (magnum for slow burners like H110)
9mm, 40S&W, 357sig, 38spl all use small pistol
357sig, uses small magnum primer.
Then you get oddballs like 460Smith that uses large rifle.

I don't think you can put smal pistol in a 45ACP unless the brass allows it. I do know some brass will allow it. I buy starline usually and they only allow large pistol.