I agree with the above. Generally speaking, 45 ACP uses 0.451" diameter for jacketed bullets while lead bullets may be encountered in 0.451" or 0.452" and the groove diameter of the barrel should be 0.451". The 45 Colt is a little different. Current guns usually have groove diameters of 0.451". Before WWII, the 45 Colt had a groove diameter of 0.454".
You may encounter revolvers made after WWII with groove diameters of 0.451", 0.452" or 0.454". What is worse is that the chamber throats in these revolvers do not always match the groove diameter. So you might have a groove diameter of 0.451" and chamber throats of 0.454". This means that a bullet of 0.454" is going to be swaged down by the barrel or a 0.451" bullet must expand to 0.454" in the throat, then be swaged back down to 0.451" in the barrel. This is not particularly good for accuracy.
Now you might also encounter a revolver with the opposite condition, such as a 0.452" groove diameter or larger and chamber throats of 0.450" (Ruger seems to be this way right now). This means that a 0.451" or 0.452" diameter bullet will be swaged down to 0.450", then enter a barrel with a groove diameter of 0.452" and it will just sort of rattle down the barrel, leave plenty of melted lead in its wake and will hit the target in a more or less higgledy piggledy fashion.
With revolvers, the ideal arrangement is for cylinder throat and groove diameter to be identical. If you cannot have this arrangement, the a cylinder throat diameter that is 0.001" larger than groove diameter is acceptable and you just size your bullets to the cylinder throat diameter.
Them 45's sure can be confussin'