Hammer swap

Swapped a SBH hammer into my Blackhawk to see if I want to have it done permanently. I love it, however while functioning it, it will only stay cocked occasionally, I understand it is not fitted, but does anyone know what's going on? Thought alot of these were fairly easy swaps? Any and all help will be greatly appreciated.

Your trigger sear may be just a tad too long to reliably catch in the hammer notch. Will the hammer move at all after you get it cocked?

Does the gun have a lighter trigger spring installed?

Does the hammer contact the back of the slot in the grip frame back strap? Sometimes they need a little filing on the back of the that slot.

They are usually a drop in but this is the 2nd one in a month with that problem.

Original spring, didn't notice it touching the grip frame, it would function normal, but just barely catch the notch, of not careful it would just fall.

Retried it, hammer not hitting frame, functions fine without cylinder, feels like it's binding with cylinder installed?

Excellent information, this helps!

With cyl removed, the hammer is allowed to go back further and therefore fully engage the sear. So the sear and the hammer slot are OK.

It has to be the cyl pawl (hand). I know you didn't change the pawl, but the slight variations of the pawl mounting hole location between hammers can make the difference.

As you said, the cyl is binding because it locks up before the hammer is fully cocked. Take a tiny bit off the front point of the lower tooth of the hand. Just remove the cyl, don't diss-assemble the gun. Stone or file the upper front point on the lower tooth of the hand. Put the cyl in the gun and see if it cocks. If not take a little bit more off.

Once you can get the hammer to cock with cyl installed, you'll have perfect timing. The cyl will lock at the same time the hammer cocks.