I'm rewatching the Naruto Chuunin exams, and in the Crunchyroll subs in episode 40, when it's being explained by Zaku's arms blew out, the explanation mentions gun barrels. However, as per this answer, there are no guns in Naruto. I don't remember the Japanese word for gun or gun barrel, and my listening isn't good enough to tell what they're saying in this particular part. Is this simply a subtitling error, or do they actually use a gun analogy in this case? If they do use a gun analogy in the anime, do they use the same analogy in the Japanese manga--that is, do they canonically explain the result using a gun analogy despite the lack of guns in Naruto?
I think the subtitles are okay. The Naruto manga does use a similar gun analogy. In chapter 70:
...Like a gun barrel when the path of a bullet is blocked, Zaku blew his arm off.
In the anime, I believe that the word that Dosu is using is 砲身 (ほうしん), which translates to "gun barrel". For context, in that sentence, Dosu was saying something along the lines of:
Actually in the wave arc wean sakura gose to the store with the bridge builder theres a gun behind the counter. Or at least in the manga there is.