Hi Ted, sorry to hear you are having a problem with your new Uberti 1858.
Did the revolver function correctly before you took it apart? Did you reassemble the revolver with the wrong hammer spring screw, wrong screw like the loading lever screw? If you used the right hammer spring screw, for the time being try putting a round toothpick in the space between the end of the hammer spring and the frame slot bottom. That will move the spring up. You could also use solid wire cut to length instead of the toothpick. That should provide a temporary fix.
I replace all my 1858 revolver springs (all 12) with the Wolff reduced power spring:
https://www.midwayusa.com/product/247241/wolff-mainspring-colt-saa-emf-hartford-and-clones-reduced-powerThere are a few good reasons to use the Wolff spring. Reduced hammer and trigger pull, ease of spring removal and insertion, and less loading on the revolver parts are benefits.
If you get the reduced power spring only tighten the hammer screw on the Wolff spring to where the screw head is flush with the frame.
Regards,
Richard