Garman picked up the food, drove there, and parked with his brights shining on the front door. He'd cut a slit in the bottom of the food bag and tucked a .38 inside to rest in his hand as he carried the package. "The .38 has a covered hammer on it, so I can shoot it in a bag. If I were to put the automatic in there, it'd jam and I'd be screwed."

I'd be screwed значит мне пришлось бы плохо?

https://dictionary.cambridge.org/dictionary/english/screwed
https://www.urbandictionary.com/define.php?term=screwed
https://idioms.thefreedictionary.com/get+screwed

если вам больше нравится, "я оказался бы в трудном/неприятном положении/ситуации"

спасибо большое! теперь понял!