Penny ballons
Long ago I used a penny balloon for barrel protector on my muzzle loader. Tight fit.
Bekeart
When I lived and hunted in cold and snowy Alaska, Washington and Colorado I would take a standard condom to place over the muzzle of my rifle to prevent getting an inadvertent plug of snow in the rifle barrel. Of course the condom had to be taped on to make it stay in place. It looks to me like these 'finger cots' would be ideal for that purpose. I love standard production items that have cross usage.
Long ago I used a penny balloon for barrel protector on my muzzle loader. Tight fit.
Bekeart