The .260 Remington is a fantastic cartridge that went obsolete almost as soon as it was introduced due to Remingon’s asinine marketing. What is not to love about an inherently accurate round with low recoil based on the .308 cartridge. I mean, ano brainer. I am stunned that the .260 did not catch on. 6.5 is THE bench rest accuracy round and now even the US military is looking at adopting the 6.5.
Oh well.
I think that it was killed by the very popular 7mm-08 Remington.
https://en.wikipedia.org/wiki/7mm-08_Remington