A gunpowder empire isn't any Early Modern empire that uses gunpowder, which would make almost all Eurasian empires between 1500 and 1800 gunpowder ones.
Rather, Marshall Hodgson (who came up with the term in his Venture of Islam series) refers to a specific type of Early Modern Islamic empire ruled by a land-centered military patronage elite, profoundly influenced by the political heritage of the Mongols and Persianate high culture, and united under an increasingly bureaucratic and unprecedentedly strong imperial center. The actual use of firearms itself is somewhat irrelevant, especially since the seventeenth-century Mughal army remained very much cavalry-focused.
Other "gunpowder empires" as Hodgson defined them could plausibly form only in Central Asia (under a more successful Shaybanid dynasty), the former Golden Horde (in an ATL where the Tatars prevail over Muscovy), and perhaps in the Arab world (a centralizing post-Mamluk regime in Egypt, a stable Maghrebi dynasty).
Many other ATL empires might be gunpowder-using empires, but they wouldn't count among the gunpowder empires.