To begin, gather river cane and bundle it and allow it to dry for up to 1 month. Choose a length between 4-7 feet. Once dried, the cane must be straightened using heat or fire just like primitive peoples have for thousands of years.
River cane tapers in diameter from the bottom up. The mouthpiece end will be at the bottom and should be trimmed a bit and smoothed over. It is best to locate the mouthpiece directly on or near a joint for added strength.
The muzzle end should be trimmed and smoothed and should have a diameter close to your thumb. A smooth mouthpiece and muzzle allow for a tight seal and a speedy release of the dart.
Next, the cane is split from end to end beginning at the smaller muzzle end. This splitting results in two halves, exposing the inner joint walls in cross-section.
The interior wall halves are then cut away and the remaining material is ground smooth. No grinding or smoothing is required between the joint sections.
All that remains is to rejoin the two halves. Hide glue, pitch or beeswax can be used. The important thing is to make sure there is an air tight seal between the two halves from mouthpiece to muzzle. Once the adhesive is in place and the seams properly joined, the blowgun is bound at points along its length using buckskin, rawhide or lengths of plant fiber cordage.
A final interior treatment is the passage of hardwood shaft with a buckskin swab attached through the blowgun several times to make sure you removed any adhesive that may have seeped to the inside.
If you live in an area that has no river cane, chances are you have some variety of giant reed grass which should work for you.