I was at the dentist the other day and read an article in Petersen's Hunting by a guy whose name (IIRC) was Joseph something. He said that very recently the .300 WinMag has over taken the 7RM in sales which was pretty shocking to me.
I've always had a 30-06 and didn't see a use in me having a 7RM or .300 WM, but several of the men I know who have only one rifle (and fit the proverb with regards to caution with such a man) swear by it and their success afield bears witness to their well placed faith in it.
I would immediately suggest that the long range hunting craze may be responsible for its decline, but that makes no sense if the .300 WM is what edged it out unless market saturation in great LR cartridges has given the 7RM more competition? I know I wouldn't choose the .300 WM over the 7RM for that purpose but I don't get all my ballistics knowledge from Petersens Hunting either...
