Depending on what I do, sometimes I take out the breechplug, sometimes I leave it in. After I clean the barrel and oil it I will take a clean cleaning patch or a pice of tape or a finger cot and cover the end of the barrel to protect it from anything getting in it. A well oiled barrel should be fine from the elements. Unless your in a area where it is really really humid, the oil in the barrel and the oil on the reat of the parts should be all you need.
(BP)