The blueprint used to produce a 3D-printed plastic gun has been downloaded about 100,000 times since going online earlier this week, according to Forbes.
Defense Distributed told the news site it was surprised by the amount of interest its Liberator gun had generated.
Earlier in the week, the company demonstrated the firearm being fired
But even before any more guns come off the DIY printing presses, there are moves afoot to ban it.
Californian senator Leland Yee said he wanted a law passed to stop the manufacture of 3D-printed guns.
"I plan to introduce legislation that will ensure public safety and stop the manufacturing of guns that are invisible to metal detectors and that can be easily made without a background check," he said in a statement.
According to Defense Distributed, most of the 100,000 downloads have been in the US, followed by Spain, Brazil, Germany and the UK.
The blueprint has also been uploaded to file-sharing site the Pirate Bay, where it has become the most popular file in the site's 3D-printing category.
It took Defense Distributed eight months to produce the firearm, which was assembled from separate components produced on an $8,000 (£5,000) 3D printer bought from auction site eBay.
While downloading the blueprints may not be illegal, any UK citizen who made and owned such a handgun could face arrest, according to the UK's Metropolitan Police.
"To actually manufacture any type of firearm in the UK, you have to be a registered firearms dealer (RFD)," it said in a statement.
"Therefore, unless you are an RFD, it would most definitely be an offence to make a gun using the blueprints. It may be legal for an RFD to manufacture a gun this way, as long as they had the necessary authorities."
One of the biggest headaches for law enforcers is the fact the gun is made from plastic - with only the firing pin made from metal.
New York congressmen Steve Israel and Chuck Schumer have sponsored legislation aimed at adding a 3D-printing provision to the US Undetectable Firearms Act, which requires all guns to be detectable.