Fuel is the step that does not divide. Low grade fuel comes in batches a single shell cannot use up, so every boomer leaves one unit lying in your inventory. Craft four shells at once and the fuel lands exactly; the gun powder was never a problem, since it splits cleanly at any count.
Behind the fuel sit animal fat and a little cloth. One decent hunt usually covers a set of four.
Only owners of the item can craft it, with no research and no bench for the shell. Mixing colours changes nothing in the sum: four plain shells, orange with red say, divide just as well. Why orange suits the last hour of a wipe is on the item page.
