The Accuracy International Remington 700 AT Chassis System, ATAICS might fit a Remington BDL in 300 RUM. However, you would need the 338 Lapua compatible Accuracy International Remington 700 AT Chassis System. It would also require some significant modification to the magazines in order to fit properly. For these reasons I recommend contacting Accuracy International in regards to compatibility with a 300RUM chambered Remington 700.