Earlier this year, Audemars Piguet undertook a "generational update" of a pivotal model within its core collection—the Royal Oak—specifically, the 38mm Royal Oak Chronograph. With the launch of the "new generation" 38mm Royal Oak Chronograph, the timepiece has been comprehensively fitted with Audemars Piguet’s new in-house Calibre 6401 automatic chronograph movement, thereby bringing a definitive end to the era of the 38mm Royal Oak Chronograph relying on outsourced movements. The Audemars Piguet Royal Oak Chronograph collection comprises two versions: a large 41mm model and a mid-sized 38mm model. Of these, the 41mm model (Reference 26240) completed its generational update in 2022, adopting Audemars Piguet’s in-house Calibre 4401 automatic chronograph movement. This year, the 38mm model has finally followed suit, completing its own update. Prior to this, the 38mm Royal Oak Chronograph had consistently utilized the outsourced FP1185 automatic chronograph movement. Given that the FP1185 movement originated in 1988 and has been in continuous use since then, its performance capabilities no longer offered a competitive advantage. Consequently, Audemars Piguet specifically developed the more compact, in-house Calibre 6401 automatic chronograph movement—tailored for the mid-sized 38mm case—to serve as a direct replacement for the FP1185. Audemars Piguet’s new Calibre 6401 features a column wheel and a vertical clutch mechanism; it measures 27mm in diameter and 5.7mm in thickness,Audemars Piguet Royal Oak replica watches.
Compared to the 32mm Audemars Piguet Calibre 4401 (found in the 41mm Royal Oak Chronograph), the Calibre 6401 is notably more compact. In terms of performance, the in-house Calibre 6401 represents a significant improvement over its predecessor, the FP1185: the balance frequency has been increased to 28,800 vibrations per hour, and the power reserve has been extended to 55 hours. Most critically, the Calibre 6401 features a modified vertical clutch structure, incorporating what Audemars Piguet describes as an "innovative caliper mechanism." In conventional vertical clutch systems, two calipers are typically employed: one is controlled by the column wheel, while the other is controlled by a separate, elongated spring. The inherent drawback of controlling a caliper via such a spring is that it necessitates greater operating force for the chronograph pushers, resulting in a stiff tactile feel and increased mechanical wear over time. Audemars Piguet has equipped this timepiece with two column wheels—both controlling the chronograph functions—thereby enhancing the tactile feel of the chronograph's operation. Beyond these technical upgrades, the "new generation" Royal Oak Chronograph 38 finally features a sapphire case back. It is worth noting that previous Royal Oak Chronograph models utilizing the FP1185 caliber never offered a transparent case back. Through this open case back, one can admire the manufacture Caliber 6401, which showcases Audemars Piguet's superlative standards of movement craftsmanship through comprehensive finishing across all components. In terms of fine details, the free-sprung balance weights are entirely "embedded" within the balance wheel itself. The balance bridge features an openworked design and incorporates the "triangular" stud holder—a signature hallmark of Audemars Piguet's new generation of movements. On the upper bridge of the movement, the column wheel is also visibly exposed. Finally, the openworked solid gold oscillating weight features a central section crafted in the brand's iconic octagonal shape.
