During my reading, I stumbled across this page describing mock battles between Su-27s and F-15s in 1992: Weapons and Technology: Su-27 vs F-15 which states:
The scheme of the mock fight was very simple. A Sukhoi was supposed to fly behind a US jet, and the planes were supposed to switch places with one another. A US plane attempted to fly away from the Russian jet, but the Russian pilot caught up with the F-15 very easily.
The planes switched places, and the Su-27 flew away from the F-15 making a turn and gaining altitude. The Russian jet found itself behind the American fighter a couple of minutes later. The F-15 pilot lost the Russian aircraft out of sight and could not escape from it afterwards: the Russian pilot was keeping the F-15 covered.
The site also gives a very brief statement about another mock battle in the year 2000, but I couldn't find anything on the internet about this sortie.
Now very little detail here is given on RADAR restrictions (if any), fuel load, external stores/weapons. However, how would an F-15 fair in a guns battle with an Su-27?
I suppose the higher TWR of the F-15 helps it in the vertical? But Kharschevsky after all, points out that the Flanker's take-off run is shorter and easier which suggests that the Su-27 has better straight line acceleration.