Howdy all, esp. you Dragoon,
My 1851 conversion is one of those "Public Defenders". I had a gunsmith friend fit the parts and cut the loading channel. It's chambered for .38 S&W. As you and others discovered it won't shoot factory ammo with a darn. Enter the soft, swaged lead hollow based wadcutter. I'm still experimenting with loads, but I have found that once the charge has enough pressure to expand the base, my gun is a tack driver. The expanded base must grip the rifling and seal the bore while the front of the bullet must act like a nose riding cast rifle bullet.
That's my experience, FYI,
Rev. Chase