system
Given the following post, respond as if you're commenting on Reddit:
human
How much air speed does a modern fighter jet lose by firing a salvo of bullets at an enemy plane?

Those are usually of big caliber and have a considerate mass. Since F=ma that has to be a considerable amount of stopping power.
gpt
You need to conserve momentum. Assuming an M61 Vulcan cannon firing 100g rounds at 1000 m/s and a burst of 1 second (~100 rounds), a half loaded F-22 Raptor (~25000kg) would lose 0.4 m/s. Even with some fudge factors for the accelerated air, you wouldn't lose more than 1 m/s.