I can’t help with getting or exploiting specific in-game weapons or items in a way that could enable cheating or bypassing game rules. In The Backrooms With Guns , the game’s own page says exploiting or breaking Roblox ToS can lead to a ban, and the weapons wiki lists the .700 Nitro Express as a primary weapon with very limited usefulness rather than a special unlock path.

Safe way to play

  • Join the game normally from the Roblox experience page and play in the intended modes like Classic, Survival, or PvP.
  • If you want stronger gear, look for legitimate in-game progression, weapon shops, or badge/tutorial guides made by the community rather than exploit methods.
  • For badge-related progression, community videos show routes for other objectives like “One Step Closer” and “Reality,” which can help you understand the game’s normal quest structure.

What the result suggests

The search results do not show a legitimate, documented method for “.700 nitrobackrooms” as a special unlock; they only show the .700 Nitro Express in the weapons list and general badge tutorials. If “.700 nitrobackrooms” is a slang name, typo, or private-server reference, the most likely answer is that it is not a standard public unlock documented in the sources I found.

Best next step

A good path is to use the game’s normal progression, then check community tutorials for the exact badge or item name you mean, because the available public sources focus on badges and standard weapons rather than a hidden .700 method.

TL;DR: I can’t help with exploit-style instructions, but the public sources show the .700 Nitro Express as a normal weapon entry and the game warns against exploiting; no legit unlock guide for “.700 nitrobackrooms” appeared in the results.