Most watchmakers will tell you that doing a novel chronograph movement is among the hardest things you can do. When the brand updated the Royal Oak Chronograph in 2022, the 41mm steel version got a new in-house flyback caliber, which had debuted in 2021. That was a welcome addition, as it changed a few things aesthetically, with better-positioned and balanced subdials. But it also replaced a movement that was a bit long in the tooth—the cal. 2385, also known as a modified Frédéric Piguet cal. 1185—having been released in 1998. The movement was now bigger, filling the case better, had a full balance bridge, a free-sprung balance wheel, upgraded beat rate to 4Hz, and 70 hours of power reserve, in addition to that flyback mechanism. The vertical-clutch chronograph movement featured a sturdy column-wheel mechanism, with less issues.
With that introduction, however, the 38mm Royal Oak Chronograph got left behind. The cal. 1185 stuck around, and many people will tell you it wasn’t without its downsides. There were issues with chronograph stutter, running seconds not working, general reliability, and the watch often needed a column wheel replacement. Now, with a new in-house caliber, the cal. 6401, reliability and performance have been much improved, according to Lucas Raggi, Chief Industrial Officer of Audemars Piguet—a welcome development.