In all my several weeks of exposure to muzzleloaders and both times I shot my rifle, I used a plastic flask that was given to me to pour powder. After the guys in the furry hats that I was shooting with stopped rolling on the ground laughing at me, they said that I will be needing a proper horn to carry my powder with. I had a horn that my wife bought me many years ago as a wall decoration, so I looked it over, reamed out the inside and smoothed it up best I could. Drilled out the measure to hold 60 grains of my homemade BP, but before I actually put powder in this thing I was wondering if the inside needs to be sealed or lined. I don't want to become a walking boom waiting to happen.
I will let the horners on the sight answer the main question, but be sure to A L W A Y S put the stopper in the horn to avoid the boom you referred to. NO EXCEPTIONS!
As an old timer in the sport I'm glad you showed up using the plastic flask whether they laughed or not. How else would you learn that there are better (more traditional) ways than to get out and join some others who have more experience?
In my experience of over 35 plus years making several hundred powder horns and examining many original horns. I have never did more than clean-up the inside of a horn with a little sandpaper. No lining of the interior is needed! I did repair a modern made horn from a fella a long time ago, that lined the horn with melted bee's wax and the inside of that horn had clumps of caked-on black powder that stuck to the corners and sides of the walls of the horn. ___ That was proof to me, why the old guys didn't line them!
Rick
Three rules -
1. ALWAYS use a seperate powder measure - never trust eyeballing, counting, or "self measuring" spouts.
2. ALWAYS place the stopper in the horn, flask or whatever...
3 NO open Flame when powder is near
and 4. __ Never experiment with homemade black powder or you will be a walking boom waiting to happen!