These missiles are more likely duds.
The reasoning is simple. Unlike standard practice of Western Airforces, in conjunction with BVR missile manufacturers, such as Raytheon, or MBDA; these Russian R-77s had NEVER been properly, or as intensively tested to ascertain its Probability Kill (pK). Neither was there any effort made to gradually improve its capabilities.
Nobody knows whether these missiles have the capability to shot down any combat aircrafts. Judging from their reluctance to buy more R-77, or fit the small numbers available on their Sukhois, not even the Russians are certain.
To make matters worse, Western Electronic Warfare Defense Suites, and Countermeasures technology have since evolved a few generations ahead since R-27, and R-77 were first conceived.
This expose another weakness: Gradual upgrades have never been Russia’s strong suit. Not even during Soviet times, when everything was meant to only be used for 10 years, before they got replaced with newly produced fighter jets, or missiles.
Anyone buying the export variant of R-77; the RVV-AE (izdeliye-190) will be sorely disappointed, IF they got to test them in real air combats.