Police and security forces around the world are buying Swiss pistols that fire a crippling burst of pepper spray, which the company claims is safer than a Taser.

But human rights group Amnesty International Switzerland questions this, saying both are dangerous and their effects unpredictable.

Unlike a can of pepper spray, the JPX Jet Protector pistol fires two 9.4-gram bursts of oleoresin capsicum, a cayenne pepper extract, with the help of a pyrotechnic charge. The solution rockets out of the barrel at 450 kph and has a range of about seven metres.

Raphael Fleischhauer, Piexon's director of technology and manufacturing, volunteered to be shot with the device during its testing phase.

"It's like getting a slash in the face," he told swissinfo. "It's a very strong pain. You can't see for 30 minutes. It stops you completely."