Tests by others have shown that water dropping is of no benefit to a bullet that is to be PC'd. The cooking temp of the pc process removes any tempering from the lead, returns it to almost original alloyed hardness (tested many times). To have a hard cast PC boolit the tin content must be present in the mix at time of casting. There seems to be mixed opinions by the "experts" as to weather a hard alloy is still needed for cast & pc'd boolits that will be driven at the upper range of cast velocities. Some have reported very good results with pure WW at over 2200 fps, some, and I don't remember the alloy content, but they rave about being able to shoot un-checked cast at 3200 fps with absolutely no leading. Personally I have only shot pure WW at up to 1700 with no leading.
Millions of pistol bullets with PC coating have been fired & satisfactorily tested so far but the higher velocity rifle stuff, with all its more complicated intricacy's is still basically in its infancy and being tested every day. Anything we can add or report on will be helpful so keep at'er boys.