n. a kind of bunk placed in banks at right angles to the wall so that the user must crawl in head first and out feet first (as in charging a muzzle-loading gun).
1919  Bunks are double and double-deckers, and some muzzle loaders.
1919  Then in other camps you have "muzzle-loaders": --Bunks arranged cross-wise of the bunkhouse (double deckers also). As the name signifies, you have to crawl into them head first, and out feet first.