What is the best way to go about building a 6mm BR Norma repeater?

I have a 98 action that is pristine and now that AICS floor plates are available for the 98, I was thinking about doing that.

How do m700 short actions work?

Getting a short fat cartridge like a BR can be a real problem with a Mauser type double stack magazine. You would be better off with a single stack magazine, like a Tikka.

The AICS Accuracy International Chassis System floor plate I am going to use will utilize a single stack magazine.

Have a look at the norma 6*47xc for what cartridge a m700 and a simple rebarrel is needed.

Built mine on a M70 SA that started it's life as a 22-250 and used the magazine block that was already installed.

The problem you may encounter is the sharp shoulder and short case. A coned breech helps a lot. Good luck with your project. I am doing a radically shortened Mauser 98 now in 6.5 BR.
Aloha, Mark