Hawg has the answer you are looking for . . . .
A .36 caliber C & B barrel starts with a reamed bore of .360 - then is rifled and as a result, you have to use a heeled bullet or a hollow base tat will expand to fit the bore - otherwise - you'll end up with leading the bore as well as "key holing" on target
A "conversion" that starts out that way - such as Uberti, etc. - the barrel is bored and rifled to the standard .357 to allow modern molds to be used - i.e. a .358 to .360 soft lead bullet. When I load 38 special (which is what your conversion will be or you can use 38 Colt Short or Colt Long) - I usually like to load them .002 oversize. I have several molds that drop at .360 and I just use them that way.