The guards let Unger handle a loaded rifle?

At the end, when the warden is urging Knauer to shoot Crewe with the rifle, on the assumption that Crewe is attempting to escape, Crewe is walking right towards a crowd of civilians; if Knauer shoots and misses, there's an excellent chance that he wounds or kills a civilian.

Ask any police officer; if they discharge their weapon in the line of duty, there's always an investigation, and one of the most important questions in the investigation is, "What was your backstop?"; in other words, what were you going to hit if you missed your intended target? I doubt that Knauer would have fired into a crowd intentionally.

Still love this movie though, despite any mistakes or flaws. One of my all-time favorites.

It could be but the rules in free society are different in prison.

They pretty much ignore the constitution and do whatever the F they want to.