The record-breaking run comes just days after the hotly-anticipated Hennessey Venom F5 was released at SEMA, aimed at cracking 300mph (483km/h). For reference, the Bugatti Chiron is limited to 261mph (420km/h) because of its tyres, but the company has suggested the car is capable of much more.
Koenigsegg conducted the run on an 11mi (18km) stretch of closed highway between Las Vegas and Pahrump with test driver Niklas Lija behind the wheel.
The road was reportedly meant to be closed for a full two days but the Nevada Highway Patrol was able to reopen it, as the car cracked the record early on day one of testing.
Racelogic recorded and verified the data over two runs, showing a peak of 284mph (457km/h) in one direction, and a two-way average of 277.9mph (447.2km/h) – 7mph (11km/h) faster than the Hennessey Venom GT managed on a one-way run in 2014.
With 865kW of power from a 5.0-litre twin-turbo V8, the car didn't sound particularly stressed early in its run. The driver only properly opened the taps beyond 300km/h and pulled 0.4G in the process.
Check out the run in the video at the top of this post, and let us know what you think in the comments below.