Ammunition made before 1990 I wouldn't leave in any of my guns for more than 10 mins after firing.
Most powders made after 1990 are fairly decent and you can let it slide for a day but no more than that.
The acids in the powder will eat away at the bore (barrel pitting).
So it's usually my reccomendation to clean your toys after you're done with them ( I know, I hate doing that too).
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Science is the organized unpredictability that strives not to set limits to mans' capabilities, but is the engine by which the limits of mans' understanding is defined-Yahoshua
  
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