I finally got around to purchasing FC3 after ED removed the LOMAC installation requirement, and I've been screwing around with the different BVR weapons available to the F-15 and Su-27. In game, flying at 25000 feet (and launching at similar speeds of around 600 knots), the R-27ER appears to get up to Mach 3.8, while the AIM-7 only reaches Mach 2.5, giving the Russian fighters a huge advantage. Wikipedia, however, suggests that the AIM-7C and onward reach Mach 4.
Why the discrepancy? Is the AIM-7 really that much slower than the Russian equivalent - and, if so, how did the military expect to win a confrontation during the cold war with them?