Already an immensely powerful machine, BMW elected to bestow its mid-sized performance sedan with even more power and reduced weight in the process. The result of all this hard work is the M5 CS, the Bavarian brand's most hardcore 5 Series yet. With 627 horsepower on tap, almost anyone would be quick behind the wheel. But when piloted by a pro driver, the focused sports sedan is a blisteringly quick car.

At the hands of Sport Auto's Christian Gebhardt, the executive sedan blitzed the Nurburgring in an incredible 7:29.57. To put that into perspective, the Ferrari Enzo lapped the track in 7:25.21. Is there another M car that can beat the incredible M5 CS? Yes, actually - and it's not the one you'd expect.

This time, Gebhardt went around the Green Hell in an M4 Competition xDrive and did it in a time that was exactly one second faster than he had managed in the more powerful M5 CS.

The M4 already has a reputation for being one of the most focused driver's tools available, but this achievement is still surprising. The M4 may weigh less than the M5 CS (3,979 lbs vs 4,115 lbs) but it is also much less powerful than its bigger brother, with a 124-hp deficit, and a consequently poorer power-to-weight ratio.

What's more, both are equipped with grippy all-wheel-drive systems. So how is it possible that the M4 is faster than its bigger brother? Well, it could be that the driver felt more comfortable behind the wheel of the nimble, more focused coupe, providing the confidence needed to push it on the technical circuit.

Gebhardt certainly looks relaxed behind the leather-trimmed tiller, feeding the C63 rival into corners with robotic precision. The hot lap is drama-free; the Michelin Pilot Sport Cup 2 tires may squeal in protest but the Bimmer hangs on with gusto.

The S58 3.0-liter turbocharged inline-six has previously been accused of lacking the aural excellence provided by other BMW sixes. However, it sings with pride while charging down the Nurburgring's straights, charging all the way up to the fairly lofty 7,200 rpm redline. On the final straight, the M4 reaches 177 mph before the pro driver stamps on the brakes.

This impressive achievement doesn't undermine the abilities of the M5 CS but actually reminds us of just how capable the latest generation M4 is. Previously, Auto Sport took to the complex racetrack in the C63 S and posted a comparatively slow time of 7:44.13 - nearly 16 seconds slower. If Mercedes wants to show the team over in Munich who's boss, the upcoming four-cylinder C63 will have to be something truly special. Thanks to clever F1 tech and typical Mercedes innovation, it's rumored to boast 550 hp and almost 600 lb-ft. But for now, we think BMW should just sit back and revel in this incredible achievement.