(slang) In an unpleasant or dangerous situation.
Used other than figuratively or idiomatically: see in, barrel.
Source: en.wiktionary.orgI think that presidents deserve to be questioned. Maybe irreverently, most of the time. Bring 'em down a size. You see a president, ask a question. You have one chance in the barrel. Don't blow it. Helen Thomas
You never get quite down to the bottom of the barrel, but we are much higher than that at the present time. There is quite a lot left in the barrel that could be explained by them. If they have some weapons, if they have some anthrax, they should deliver that. Hans Blix