It's only a good deal of you *want* it, otherwise you are buying on price alone. If you like to flip stuff to try to make money, I suppose that works. I personally don't as my time is worth more than that and I don't really like selling stuff. If I did I would open a gun shop.
Do you have any other 6mm Rem's? I have a 6mm M700 and like the cartridge, but factory ammo is scarce, limited in choices, and expensive. Reloading fixes that but you have to get and be able to replace brass. Usually that isn't a problem with 6mm (it was tougher a few years ago) but you I'll pay more for it, so it may be cheaper in the long run to get a .243. Again, the cartridge is slightly superior to the .243, but I would probably devalue an 6mm $100 over an identical .243, but that's just me (and I own a 6mm and a .243). Also, you may have a harder time selling it if you want to be rid of it down the road.
