Its a dead cartridge, no longer chambered by any major rifle manufacturer. I have one and love its accuracy. Its chambered in a custom 17 lb 1000 yd BR rifle. I have brass supply to last this barrel but don't know if I'll use the reamer again.
Should be fairly easy to neck down annealed 300WSM in a 7WSM die and carefully adjust sizing depth to a point where you can feel bolt close on false shoulder. I would recommend some care be taken to determine if case necks need outside turning. Annealing properly is the issue. I use 300WSM to make a long-necked 25-SAUM, requires moving shoulder back and necking down. This is done in one step using a FL RCBS 25WSSM die adjusted to proper length. I realize the necking down and moving shoulder back isn't the same as creating a ridge on a case mouth and fire-forming shoulder forward to fill chamber. Annealing neck and shoulder area is critical, needs to be done right. If using 270 WSM brass I would recommend you neck up to 300 WSM then down to 7mm.