Agree. #00 Buck is 0.330" (#000 is 0.360") so it is very possible you have buckshot rather than a single projectile. Buck and ball loads were very common in New England with one bore sized ball and three smaller ones. Also used for night picket duty in the Civil War.
Thanks Breezie, it was tough to find because it is so tiny. I kept picking up handfuls of dirt, using my pro pointer and it eventually made into my goodie bag.
The model 1851 Colt pistol is .36 caliber. Use calipers to check it's size, an unfired pistol bullet for the 1851 cap and ball revolver would be .375 of an inch.