The major fight scene is the Battle of Abu Klea, which took place on January 17, 1885. A British Desert Column of approximately 1,100 troops fought a Mahdist force of over 12,000 dervishes. The scene depicted in the film, however, is a fictional version of the actual battle.
When Jack is chasing the sniper, the sniper is shown running through an alley way with two adults and a child in front of him. After climbing onto the roof, jumping off, and climbing a couple of walls...he is shown again in the same scene running through the alley with the same three people there.
When Harry loses his horse and has to jump onto the back of a free one, you can see the rider next to it holding its reins so it will keep running. There is no reason for him to be doing this in the middle of a charge, except to have it ready for Harry to mount.