I was curious and scoured the internet, but came up empty. The BLRs were chambered for both the 7mm Rem Mag and the .300 Win mag. It wouldn't be too much of a stretch to re-barrel one for a .264 Win Mag, but I could not turn up any mention of anyone doing so. I also have to note that over the last 60 years or so I have repeatedly heard of odd chamberings in rifles that were not and could not have been so chambered. People often get confused or misremember--even Me!