Some of the earliest .45acp revolvers had cylinders that were bored through, meaning you had to use clips to contril headspace. All the ones I've seen, both S&W and Colt, had actual headspace ledges in the chambers. These you can shoot with loose .45acp rounds, you just have to pick, pry, or poke the empties out.
The sole Colt 1917 I've got to spend time with had a really heavy trigger, and it wasn't much fun to shoot double action. Smiths I like better in that regard. My remaining .45acp revolver is a S&W Model 25-2. After some work it has a very nice trigger.