The Wraith handblasters are handy little weapons, being capable of stunning most humans with one shot. Even though most humans get incapacitated for some time after a single shot, strong humans who have experienced the effect of the stunner on several occasions are usually more resilient. Ronon Dex, being an extreme case, has been able to withstand three blasts before going down, and the effects don't last very long on him. The Runner Kiryk was also resilient. Wraiths usually need two blasts to become incapacitated.