I use a piece of Masking Tape cut in a circle about the size of a quarter or a tad bigger. I wipe the muzzle end with alcohol befor I apply it to the end and it sticks great, keeps out moisture and debris and you dont have to remove it to shoot. I just overlap the Tape slightly over the Muzzle End and work in around it.
And no I have never had a pice of masking tape get (puntcured) by anything and I go into some thick brush. Also Rain and Snow have no effect on the Tape it's pretty durable.
Now I know some use Finger Cots or Barrel Mits BUT when applied they (cover) part of the front sight on the Barrel, and if you need to use your Open Sights the Muzzle Mit or Finger Cot is in the way, the Tape is not seen when looking through your sights. A roll of Masking Tape is cheap and I think the last roll I used took me about 10 years to use up.
(BP)