When I cut down standard Colt SAA mainsprings(to correct length) and installed them in both the Uberti 49 Pocket and Pocket Navy, almost all(about 90%)of the cap jam problems went away. I had also installed Slix Shot nipples. However, I was left with both guns that were, to me, too difficult to cock and may lead to premature wear on the internal parts. I could have thinned down the mainsprings, but I saw where Taylors is having a two for one sale on Uberti SAA mainsprings. These are lighter than the Colt mainsprings I cut down but should still be heavier than the original Pocket mainsprings. They should be in tomorrow so I should be able to quickly adjust the length to fit the Pockets and test soon.
By the way, some have mentioned just "flipping" the muzzle to clear the caps, but in this case it doesn't apply. What is going on with my two guns(and others reporting the same problem) is after firing a shot, the hammer blows back and sucks a cap back with it which lands down in the hammer channel. At this point the hammer is now not quite at half cock and exerting pressure against the fired cap. At the very least you have to cock the hammer a bit more and try to clear the cap. Frustrating, and really points to a mainspring that is too weak.