Fitting a replacement bolt in a Colt SAA has caused me to spend many many hours nearly every time I have done that task.. In your case, it sounds like the bolt is not 'dropping' soon enough to allow the cylinder to rotate. There are probably a few ways to attack that problem. It may be that the cam on the hammer is not engaging with the arm of the bolt soon enough. That MIGHT mean that you made the 'dished out' portion on that arm a bit too deep. Of course you might be able to compensate for that by removing a bit of metal from the top of the bolt that fits into the cylinder stops. There are probably at least a half dozen other issue that could be causing your problem. GOOD LUCK!