I'm planning to do this very project as soon as I finish my degree next year. I've already been researching this project for almost a year now and I've learned a lot. This is probably the only way I'll ever be able to afford a double rifle. I may catch a lot of flak for this but I plan on using a Stoeger 12 ga. action (unless I find some reason to change my mind). Many of the others that people recommend as being suitable are way out of my budget. I can afford $1000.00+ for an action about like I can afford a new double. They might as well be a new DR. I'll build a clamping fixture to test fire it in when I get to that point. If it blows up then it blows up. Afterall, it's as much about the journey as it is the destination. I plan on chambering either 450/400, 500/416, 450 3-1/4", or 450 No.2. A lot of it will depend on which ones I can find reamers for. If you decide to start yours keep us posted along the way.