Hi, today I received my new 5-1/2" Pietta 1858 that I purchased from Cabella's recently. The revolver is perfect and well timed with the cap and ball cylinder. However, this revolver has the same problem with my two Taylor (R&D) 6-shot conversion cylinders that I had with the three other Pietta 1858s that I purchased last summer. It appears that this problem is systemic with current production Pietta 1858's.
The problem: The revolver with the conversion cylinder full cocks properly with the bolt locking the cylinder in place. However, if the hammer is let down after pulling the trigger, the bolt unlocks as the hammer moves forward. As the hammer gets close to the cylinder end, the bolt rises again far away from the cylinder bolt slot. This is a very unsafe situation that could get a shooter hurt. This problem occurred for all of my four Pietta 1858 purchased over the last eight months.
The reason for this problem: The bolt slot depth of the cap and ball cylinder is 0.063". The bolt slot depth of the Taylor (R&D) 6-shot cylinder is only 0.026". When the bolt rises on Taylor cylinder it is prevented in rising high enough such that the bolt leg can pop up on the hammer cam. Pulling the trigger then has the hammer actually draw the bolt back out of lockup on hammer fall. Sometimes the cylinder even rotates counterclockwise as the hammer is falling.
The solution: Without changing the revolver timing, a fix is necessary to have the bolt leg pop over the hammer cam with a very small bolt rise as with the conversion cylinder. A similar situation can also occur with the Colt 1873 SAA. The solution for the SAA is to bevel an edge of the bolt leg. The same fix can be applied to the 1858, but the bolt leg is a bit different than the SAA. A very small amount of metal is stoned off the 1858 bolt leg without (note without) changing the bolt leg length. If you change the bolt leg length, the timing will change, something you don't want to do. The following photos show an original bolt on the left, the modified bolt leg on the right:
When doing the stoning remove only a small amount of metal and test. Your initial testing (with cylinder removed) can simply be done by limiting the bolt height with your finger and pulling the trigger as the hammer is let down. As you keep removing metal you will notice that the bolt stays up more and more as the hammer is let down. Go easy and don't overdo the beveling because you could get to a point where the bolt doesn't retract on cocking.
Worst case is that you totally screw up your bolt. You can buy them from VTI for $15 (however, they are currently out of stock, expect more in 6-8 weeks). If you are a bit nervous about doing this yourself, you can either send your revolver to Taylor, or maybe talk them into sending you a modified bolt.
Remember, go slow and test often.
Another potential problem is the bolt/trigger spring bolt length. Pietta has lengthened this screw where it may rub or interfere with the conversion cylinder. The bolt end should just be flush with the frame. Shorten by filing this screw if necessary. Three of my Piettas needed this adjustment.