In shotguns and shotgun shells, naphthalene is the compound whose escape from the barrel or the shell is most suitable for monitoring the time since the latest discharge. Additionally, an unidentified compound, designated as TEA2 compound and detected with the TEA detector in the GC-TEA system is useful for determining the last discharge. In the current study, rifles of various calibers charged with ammunition from various manufacturers were subjected to SPME sampling. All the experiments resulted in the detection of the TEA2 peak inside rifle barrels one day after the shooting, which was the shortest studied time after discharge. The amount of combustion products detected inside a firearm immediately after firing will be, of course, much higher. The amount of the TEA2 compound decreased with time after discharge in a manner similar to that observed for shotguns and spent cartridges. Like in shotguns, there are differences in the amount of the TEA2 compound deposited in firearm barrels on shooting with ammunition from different manufacturers; however, these differences are lower for rifles. The sampling was performed both from the muzzle position and the breech position one day after the shooting with various kinds of ammunition. The decrease of the TEA2 peak with time after shooting is nonexponential, and the curve-fitting procedures proposed for the estimation of time since discharge of shotguns can be applied also for rifles. 2 tables, 5 figures, and 3 references