Here I am.
With both of them being 50 ft away (I use the metric system so about 15.24 meters), the hunter outranges by a bloody ton. Assuming his equipment AP is around 35 MJ (unless I'm wrong since I checked up the calcs of the verse), Black Sun can close the distance fine enough if he plans to just tank the fire, due to the dura diff of 50.9 MJ. He will obviously dodge and use his blade to parry the bullets coming his way and even with speed equalization, Kotaro's reaction speed is still faster. Class M against an above average human LS is going to be extremely problematic for Old Hunty here and not only that, but his durability also makes it that one pat from the bugman will knock him out stone cold. Since it's Black Sun, he'll obviously go for incap against the hunter like a throw or something to defeat him so there won't be killing involved.
We have to get the camouflage out of the way, because that really won't make much of a difference honestly, due to Black Sun's two enhanced senses and extrasensory perception. He's going to pick up light intensity, humidity, vibration, wind velocity among other things while also having a greater field of vision with his compound eyes and antenna, and that's from his kaijin form one. His rider form will allow him to see clearly from 800 meters away, even in dark places. His antenna should now be upgraded to detect subtle changes in the environment, such as air currents and temperature, as well as the source of the attack, allowing for swift evasion and defense, and paired with his extrasensory perception that lets him detect presence hiding in shadows, murderous intent, and approaching danger, it won't be long before Black Sun is back at the chase for the hunter should he even get the chance to hide away from him, which would probably be slim.
Close Range is where Kotaro will dominate, since he'll be going for breaking any and every single one of his weapon he gets his hands on, before he deals the decisive blow to knock him out. The few wincons the hunter has is to successfully evade him while shooting as much as possible and have his tranquilizer hit Black Sun, since he doesn't resist sleep manip at all.
Other than that, I honestly see it as a low to possibly maybe half-mid diff win for Black Sun.