Gukgung - Korean Archery

The traditional Korean bow is a highly reflexed version of the classic Eurasian composite bow. The core is bamboo with sinew backed to prevent the bow breaking and to add a pulling strength to the limbs, with oak at the handle. On the belly is water buffalo horn which significantly increases the power by pushing the limbs. This combination of horn which pushes from the belly and sinew that pulls from the back is the defining strength of the bow. The siyahs, the stiffened outer ends of the limbs, are made of either mulberry or black locust spliced (v-splice) onto the bamboo. The glue is made from isinglass. Over the sinew backing is a special birch bark that is imported from Northeast China. It is soaked in sea water (possibly for one year). It is applied to the back using diluted rubber cement (using benzene as the solvent). No sights or other modern attachments are used.
The draw weights vary, but most are above twenty kilograms. Competitions, either bow may be used, with carbon-fiber arrows, but for national competitions, only the composite bow and bamboo arrows may be used. Korean archers have also been very successful in Olympic and other competitions with more modern types of bow.
The sukgung, a kind of crossbow, and the Gak-gung are a small but very powerful bow. A sukgung can shoot up to 400 meters while a Gak-gung can shoot up to 350 meters.

http://shootarrows.blogspot.com/2014/10/what-is-korean-archery-guk-gung.html