SAHIBABAD, India—On the outskirts of New Delhi, in a cramped concrete workshop where the air shimmers with the light of welding torches, a young Indian businessman has become a master craftsman of Napoleonic swords.

And medieval chain mail armor. And World War II hand grenades and helmets.

From Hollywood war movies to Japanese Samurai films to battle re-enactments across Europe, Ashok Rai, 31, is one of the world's go-to men for historic weapons and battle attire.

Rai's workshop reverberates with the sounds of metal being hammered and beaten into chain mail, swords, axes, muskets, sabers, spears and helmets.