If there is plastic in the barrel, then you need to get a good nylon or brass brush and some solvent. I use Montana X-treme Cowboy Solvent. Another solvent that works good is Birchwood Casey Bore Cleaner. Some people take the barrel off the stock and use brake cleaner. Be sure and do the brake cleaner outside.

After you apply a good wet patch of the solvent, I like to dip the brush in the solvent and then push through the barrel and then pull back up. Don't work your brush in short strokes.

After brushing, run a couple more solvent patches through. Then check the barrel. You plastic should be gone. Now dry patch the solvent out of the barrel and then since you are going to store the rifle... saturate a patch with a good gun oil. Swab the bore in short strokes until the bore is well covered.

Be sure to wipe down ALL parts and put them back in the rifle. There is no reason to pop a 209 through it. Let the oil sit in it. Wipe the outside of the barrel off and put the gun back together.

When you bring it out next, alcohol patches working over the rifle will remove the oil. Then you can pop some primers to blow the oil out of the breech plug.

Also I like to check my rifles every three months when they are stored to make sure they are ok...

And I bundle up and shoot when it is cold too. I hunt in the cold. I shoot in the cold. A good brisk day is a great time to shoot the rifle.