You didn't say which company made your 1860 Colt and it may make a difference.
If it was made by Uberti it will have the Uberti trademark on the frame. This consists of the image of a rifled barrel with a capital U in the middle.
If the gun was made by Uberti it should have .450 diameter chambers (according to Dixie's catalog) and the .450 diameter bullets your mold will cast will be a light push fit into the chamber mouth.
Perhaps too light because although they should seal the chambers if some grease is applied to the grease grooves the loaded bullets may "jump" forward due to recoil when the gun is fired.
If that happens it will lock the cylinder and prevent the gun from operating properly.
If the gun was made by Pietta, Dixie's catalog says it will have .446 diameter chambers.
These should work with your .450 diameter bullets but they may be difficult to ram with the guns loading lever.
As to the type of bullet from the mold your buying, I can't say if your bullets will duplicate the originals or not.
The original bullets were called "heeled" because the lower area below the bottom grease groove was slightly smaller than the main body.
This undersize area pilots in the chambers and aligns the bullet so that it will not be canted and will shear off lead from all sides when it is loaded.
As for loading pressure, any bullet will take much more force to load than a round ball, even if it is made from the purest lead.
The 1860 Colt reproductions barrels are left soft or unhardened in the area where the holes that the teeth of the loading lever engages it.
We have had more than one person on the forum say that the barrel holes were damaged by the loading lever teeth when they were loading balls that were much larger than the chambers mouth and loading bullets would take even more pressure.
If your determined to shoot bullets in your Colt that's fine but I thought you should be aware of the damage that may be caused from their use.
