I can buy an 7MM mag and have the chamber redone to hold an 8MM mag casing rather than paying $800 to buy one from remington, correct?

Yes you can rechamber a 7mm Remington mag barrel to a 7mm STW.

As far as cartridge dimensions go, that should work fine. There is one thing that must be taken into consideration though. Make sure that the 7 RM has a 26" barrel, and that the 7 STW cartridges will fit in the Magazine. I am not sure of what manufacturers make a 7 RM with a 26" barrel, but the 7 STW would need it to take full advantage of what the cartidge is capable of. If I couldn't find a 7 RM with a 26" barrel, then I would either just keep it 7 RM or buy the 7 STW. I am no expert, so I don't know if you would run into other problems with internal pressure, etc, so I would definately as a couple of competant gunsmiths before having this kind of mod done to a rifle.

Before the 7mm STW was considered a wildcat, I wanted to do the same as you. I spoke to quite a few gunsmiths, and the majority suggested the use of a Ruger #1 due to its single shot action. There isa Ruger #1 Standard 7mm Rem. Mag. athttp://www.gunsamerica.com/guns/976499186.htm for $735.00. You could probably use a T/C Encore 7mm Rem. Mag. Good luck.

Some of the 7MM Rem mags would work and some would need alteration to the Magazine box to hold the STW. Be sure to check out that possibility.

Find a model 700 with a 26" barrel in 7mmremmagand the conversion is very simple.

I thought the 700 Rem was one that worked but didn't recall for sure.