Standard bullets for both - -
.45 Colt and .45 ACP are .451 to .452. I believe most of the jacketed bullets are .451 to .4515, while lead are usually sized to .452. You have to special order .454 and .455 lead bullets from commercial makers.
Many years ago, Winchester/Western, at least, standardized their old style .45 Colt bullet as a .452" diameter copper washed "Luballoy" lead bullet. It was a round nose design with a very small flat meplat, and a hollow base. Being relatively soft lead, the HB would open out nicely to fill the .454 bore of Pre-WWII barrels, and yet not leave big lead deposits in the tighter-bored postwar barrels.
Several years back, I bought a nice old Colt New Service in .45 Colt. I was very disappointed to find that my pet handloads didn't group worth a hoot when fired in it. I was using fairly hard cast bullets from a Lyman 454424 mould, sized at .452, at about 850 fps. I did well to stay on a sheet of 8 x 10 paper at 25 yards. I had about 40 rounds of old Western factory ammo with me at the range, though, and THAT stuff shot very decent groups. Finally figured it out . . . . I special ordered some 250 gr. LSWC bullets, sized .454, and they shot well in the old Colt.
I shared my new-found knowledge with some Cowboy Action Shooters and was greeted with wry smiles and rude snickers. Many of them had been shooting pre-war SAAs for a long time, and it seems I was the "last kid on the block" to learn this gem of wisdom.
Best,
Johnny