First of all, I'd like to say that this instructable is loosely based on arpruss's Blowguns and paper cone darts.here is the link, https://www.instructables.com/id/Blowguns-and-pape...
Cutting mat and ruler,
8 1/2" by 11" lightweight paper,
Step 1: Cut the Paper
Cut the paper in half lengthwise (about 4 1/4") with the exacto knife.
Step 2: Rolling the Paper
Next your going take the rubber band and wrap it many times around the pensile near the eraser end.
If your paper has a design on it put the design on the bottom.
Now, fold the paper over around 1" from the end (but don't crease it!)
Begin rolling the paper, leaving a big flap at the end.
We need to tighten the cone now, while still holding the dart near the tip,
gently put a finger into the hole and roll into a cone shape
Step 3: Tighten More
That tighten it a little but we need it to be tighter,
to do that we are going to insert the rubber band pensile eraser end first and twist clockwise.
Step 4: Seal and Size
Tear off some strips of duct tape and press the flap that is left onto it.
Now your going to roll the dart over so the duct tape seals it shut,
and holds it in place.
Next you can place the other strips on the dart to make it stronger.
To size the dart insert it into the blowgun until right before it stops and draw a line
Then use the scissors to cut off the extra length.