No. 27 is great for working on technique in the middle range, particularly slurred/tongued combinations. Suggested tempo is quarter=96, although it’s a good idea to practice slower to make sure that the last sixteenth note in a slurred group is not clipped. Exaggerate the dynamic changes as much as possible.  Play with all repeats for endurance practice (this goes for all Kopprasch).  Here’s some more advice from The Horn Handbook, by Verne Reynolds.

Etude No. 27 is another study in slurred and tongued notes within a rhythmic group. Be sure to play a full quarter-note when it is the last note of a phrase. [p. 60]