Step 1: Fixing the jamming
the reason the gun jams is because the barrel spike squshes your dart against the slot the spike would normally slide into. to fix this problem, we're going to add an additional cover so the dart cant be pushed out of the cradle to were it can get jammed.
cut a piece of your ice cream lid to the length of the cradle which the barrel spike slides between. cut the width of the plastic long enough so that the ridge of the barrel spike can still slide between, try not to make it too tight though.
You'll need to bend the plastic so it fits nicely, i heated the plastic with a lighter to make it easier to bend.
Round the top corner edge on each piece of plastic closest to the spike.
hot glue in place.