From the Wiki place:
Frankford Arsenal FA-70 primers used potassium chlorate as an oxidizer for lead(II) thiocyanate, to increase the sensitivity of potassium chlorate, and antimony trisulfide, as an abrasive, with minor amounts of trinitrotoluene. These corrosive primers leave a residue of potassium chloride salt in the bore after a cartridge is fired. These hygroscopic salt crystals will hold moisture from a humid atmosphere and cause rusting. These corrosive primers can cause serious damage to the gun unless the barrel and action are cleaned carefully after firing.
If you are out in the desert (or in Sacramento in the summer) you would probably be OK to wait until you get home after a weekend of shooting. I personally pour about a pint of water through a funnel down the chamber of the Mosin Nagant. It is usually so hot that the first few ounces boil over so I do it very slowly. After the water is out, I run a couple of patches to ensure the bore/chamber is dry, then spray some CLP or Rem Oil down the bore and run another patch through. Clean as usual the next day or next weekend after going home.