1st. Determine if any mods are affecting the weapons in game, using proccess of elimination. Yes; Determine if there was an error in installation of the mod, reinstall if there was, and if there wasn't, deactivate the mod altogether. No; Move to the 2nd Course of action. 2nd. Determine if there is anything wrong with the original weapons, using G.E.C.K. Load only fallout3.esp If Yes; Back up your save files/mods and reinstall Fallout 3/fix it if you know how. If No; Move onto the third course of action. 3rd. Find out if any mods are conflicting with this. Open fallout3.esp and your most recent mod using the G.E.C.K. Check the weapons. Repeat on mods most recent to last. If yes; Deactivate the mod, or uninstall it altogether. If No; Move on to step 4. 4th. Bash your head against the keyboard until fallout 3 fixes itself, or someone with more experience answers.