During his live appearances, all of Byron's shots are between 10 and 15 yards. He says he wants to keep them at hunting distances. I have seen him live several years ago, and he is amazing! His vision has to be almost super-human.
As to Gene and Barry shooting aspirins out of the air at 30-50 yards...no way! I would believe 30 to 50 feet (15 to 17 yards), which would still be an amazing feat of archery. Glue an aspirin to a sheet of black paper, then back up to 30 yards and see if you can see the aspirin.
Although age has diminished my vision some, when I was flying planes, most of the flight physical dealt with vision. Their charts went to 20-10. I could go beyond that, but they just put down 20-10 because they weren't sure exactly what my acuity was. My point is my vision was beyond excellent, but I'm sure I could not have seen, much less hit, an aspirin at 30 yards even when my vision was at its best.
What impresses me the most about guys like Byron, Gene and Barry (and I'd add Ron Le Clair) is the hand-eye coordination they have to go along with their incredible vision. Most of us would have trouble hitting a tennis ball tossed at 15 yards, much less an aspirin! Granted, they have done more shooting than the average archer, but I think their ability goes beyond what simple practice would provide.
If you ever get the chance to see one of those guys shoot (not on TV or video but live), take it!