There are lots of things to put over the muzzle of the rifle to keep water out. I use finger cots. You can get them at Wal Mart. Get the large size. They will roll right over the end of the barrel and no moisture can get down there. Just be sure to pull it at the end of the day and wipe the area down with oil on a cloth patch.

I have used plastic tape over the end of the muzzle. I have used balloons and handi wrap. All of them do the same thing. The reason I went to the finger cots are I can carry them easy, and they do the job.

These things will not effect the accuracy. If you have doubts try them on the range. Just remember that nothing can be used that actually plugs the barrel. I say this because I saw a person once with a cork in the end of the muzzleloader. I just did not think that was a good idea.