In addition to the mentioned will, we have information from various mortgages, the latest dated 1772. The most slaves that we can account for so far is six. Sharper, of course, and Cork, Rudham, Tom, Dinah, and Judah. An earlier mortgage lists London, but he is missing from the 1772 list.
Unfortunately, we have no information regarding any conveyances. Since subsequent generations of Ragins had so many slaves, my guess is that they tended to stay with the Ragin family. A mild exception is the will of Charles C. Ragin, but that was two generations after the mention of the Broughtons in the earlier will. I wish we had better information but we do not.
Incidentally, to respond to earlier speculation, my understanding is that William Ragin came to the Colonies with Richard Harvin (II) ca. 1740, Irish Catholics fleeing the penal codes of the Irish Protestants. They stopped in Newberry for a while before moving on to Sumter district. (For some reason, Newberry, SC, attracted large numbers of Irish settlers). Both married Lucys, ancestry unknown, although one marriage record shows William Ragin marrying Lucy Ragan -- it could just be a transcription error.
Good sources of genealogical information for this area are the Mill's Atlases. They are dated around 1825, based on surveys of 1815. I searched for a Broughton holding on the Sumter district map, but found none (yet). However, since the Ragin holdings are close to the southern edge, it is conceivable that the Broughton land will be on the Orangeburgh district map (or one of the others). Unfortunately I have been unable to locate these other maps online.
Another good source of information is the Singleton family genealogical website. The family has holdings all over the northern portion of the Sumter District map, and their site catalogs a large number of Broughtons.
I'm probably listing info you already know, but I hope this helps.