After any hammer bobbing, be sure to do all the safety and function checks, then take it out and shoot it, a full box of whatever you plan on carrying it for self-defense, to ensure that the lightened hammer is NOT going to result in light firing pin strikes. This can happen on any revolver.
You could bob the hammers on 100 guns of the exact same model, with sequential serial numbers, and bob the hammers exactly the same amount, weighing them and they weigh within .1 grains of one another, and a percentage of them will then have light firing pin strikes and not set off a cartridge 100% of the time.
The difference is in the hammers fit within the frame, and the friction that results from that fit.
If the friction is high, the heavier (pre bobbing) hammer (assuming the gun was 100% reliable in ignition prior to the hammer bobbing!) will have enough energy (velocity squared times the weight of the object moving, same equation as for a bullet's muzzle energy or down range energy) to set off the primer.
But if you lighten the weight, while you might think that this will speed up the hammer's flight time (which should affect its energy), it doesn't always. It may not speed it up enough to equal the energy it formerly had.
I've had a few that slowed down, a lot, and didn't set off the primers with 100% reliability.
The spring was delivering the same energy, and with the lighter hammer, it should move faster and still generate enough energy to set off any primer, but if the spring now has too much energy for the light weight hammer, and you have done nothing else to the action, you may find the hammer now slows down because it is being driven forward and slightly sideways, so it now has friction in the frame it didn't have before. So you may need to replace the spring , with a lighter one, or even with a heavier one.
Just like with a firing pin in a bolt action rifle for example where for the greatest reliability, fastest lock time and greatest accuracy, the firing pin should be perfectly centered in its tunnel, and that tunnel perfectly centered with the axis of the bore, well, a revolvers hammer should be perfectly centered in the frame opening.
If it's not, then it's rubbing somewhere, and that slows it down. The cure for this is generally polishing the sides of the hammer and the insides of the frame and fitting an oversized pivot pin to the hammer to eliminate all side slop, along with polished washers on either side of the hammer pivot (sometimes off different thicknesses on each side to get the hammer centered) to get rid of the slop and allow the gun to function properly and maybe gain a tiny bit of accuracy.
You just don't know what's going to happen when you alter any component in a gun's cycling until you test it.
You can make guestimates, but that's about it.
So, if your life is going to depend on it being 100% reliable, after you do anything to a gun, test it with a fairly large amount of the ammo you intend to carry it loaded with.