I have about 80 hours on Veteran, not once have I gotten close to this penance being completed. It requires either insane discipline, practice, and immense familiarity with your weapon… or just a complete disregard for others by not using a ranged weapon for over half a match after burning it all on one horde. Veteran’s whole kit revolves around their ranged weapon, it allows for you to kill priority targets before your teammates need to worry about them. This penance, when completed with all the recommended tactics (other than just playing a different character), restricts your loadout to the point where a lucky level 10 can outshine you.
The fix for this is easy too, just lower it from 100% accuracy to 85% to 95%. Give some wiggle room for people who aren’t going to hit their shots all the time, or people using a controller. Alternatively replace it with something that couldn’t hinder the team as much, such as “Kill 25 designated targets in 60 seconds on Heresy or higher”, “Get 100 kills without moving on Heresy or higher”, or “Contribute to 50% of the grenades thrown in a mission on Heresy or higher”. Anything would be preferred to the current penance.