Some of the smaller ones look like old airgun pellets.. If they have a hollow in the back, i would say that they were definately that.
Cant really tell from the picture.
From measurements I made from your photo,those bullets are about .30 caliber.Well, there were so many kinds of revolver and small rifle cartridges from around 100 years ago that it would be hard to guess what they were fired from.The two with fat noses were probably fired into soft dirt.The pointy one,well I've never seen one like that!
The smaller ones appear to be post war I've found similar ones in every patch of woods I've dug in. One way to Identify is with the crimp marks located at the base most modern day bullets have that to lock them into the shell casing. I personally have never seen anythin Civil War with the crimpings but not saying there may not have been some though.