i use this "trick" all the time. in fact, Birchwood-Casey makes a "gun condem" just for that reason. those work fine on smaller bore guns, but in the cold, with big bores, they often rip apart leaving the barrel wide open. i typicly use electrical tape. but i think any light tape would work just as well. i do not think i would try duct tape, there might be enough resistance with that to seriously mess things up. my experience with electrical tape has been favorable. no blown up guns, and accuracy has not suffered any appreciable amount over the distances i shoot. if you shoot long range, i would definitly check the accuracy befoe i went hunting. it would be awefull to have a trophy buck all lined up, and miss, or worse, gut shoot him because of the tape at 400 yards. i would think a baggie taped or rubber banded would work just as well also. all you are trying to do is keep debris out of the barrel.