Glad to have beeen of some help.
The Doug Johnson article is excellent and is probably the best summary to date of the Egyptian Army of the 1880's but, like you, I believe the reference to a 6.5 cm Krupp is suspect. A quick look for any other reference to a Krupp gun of this calibre gave a zero return, although there was a 6 cm. Mountain Gun produced in the early 1870's, I believe. Any 6.5 cm gun in the Egyptian Army of this period was almost certainly one of the brass mountain guns cast at the Cairo Arsenal and used extensively in the war against Abyssinia in the 1860's but starting to disappear by the mid-1880's. It may be that the word " Krupp " simply became synonymous with an artillery piece and was applied to any gun. The Metric System was unfamiliar to many English-speaking writers of the 19th ( and 21st! ) century and even the sometimes pedantic Lord Wolseley makes reference to a 9 cm Krupp being fired by the Egyptians in 1884 when, of course, there was no such gun.
The photo of the Egyptian gunners depicts a Krupp gun, the breech is a give-away, and it is almost certainly either a 7.5 cm or a 8.8 cm example. As the men are wearing their blue uniforms I would take a guess and say that it was taken at the Artillery Depot, either at the Barrage Barracks or Abassayieh Barracks, in Cairo. Certainly on campaign during the 1880's and 1890's the artillery was pulled or carried by horse, mule or camel, depending on the terrain, and not man-packed.
Maybe one of our artillery experts can shed light on the efficacy of trundling a gun around the parade square? It sounds like just the sort of activity for young soldiers!
ps: By the way, the photo above my name, to the right, is that of a be-medalled Egyptian Artillery Gunnery Instructor. The artillery were generally regarded as the most professional branch of the post-1882 Army ( I refuse to employ that greatly over-used word " elite. " They were just good and they knew it. )