I have a couple of 'switch' barrel rifles. I typically dont use them as switch barrel but it is nice to be able to take them apart and have them go back together easily.
My 338 Edge has two barrels. 1: 300 RUM and 338 Edge. I dont switch to the 300 anymore but I use to.
As far as removing the stock it largely depends on what contour you use. Obviously a cylindrical barrel wont need stock removal. My 300 and 338 barrels are similar to the M24 contours and the stock does NOT need to be removed to switch them. If you use a douglas or sendero style taper or similar, you will have to remove the stock to switch barrels. Or a very steep straight taper for that matter depending on how wide a barrel channel is in the stock. For M24 contours you can maintain a fairly tight channel and still switch barrels without stock removal. Even if you did have a sharp taper by the breach, I assume you could have some stock material removed forward so you would not have to remove the stock.
As far as the scope, again it will depend on contour and scope height. For straight tapers you will not need to unless there is only a few thousands clearence and the objective is way out there in frot of the action. If you have a sendero style or similar and the scope bell is ahead of the radius and you have low clearence, you will have to remove the scope. As long as you keep good clearences, you dont need to remove the scope. I did however one time scar my sun shade by bumping the threads against it so be carefull.
Not sure about lubing the threads. I never did and did not have a problem but not sure if you are technically suppose to or not.
Keep in mind when using two barrels of different calibers that the different cartridges need to share the same size base for the bolt face or you need two bolts. One for each style case. Also, feed rails for a given case diameter can dictate how well the rifle will feed a cartridge of a different caliber if used as a repeater.
Hope that helps!
M
