I am not familiar with the 7 mm STW and I do not have my books with me to see the size. I am guessing you will want the long action 200 to accommodate this cartridge. That is a 30-06 or 7mm Magnum case. If your overall length is not more than the 30-06 or 7mm Magnum it should cycle through your action. I just thought of the head size. If it is not a standard head size, 30-06 or 7mm Magnum then you will have to have a head machined to fit it. Again I do not have a book close to check. If it is very much longer than a 30-06 then you may not even be able to single feed the 7mm STW. I have changed out a few barrels. Having the go - no go gages is all you need for head spacing your barrel. I have set head spaced with a full length sized case, but prefer the go gage. I set mine to the minimum so I have felt no need to have a no go gage. As far as torque - when I set a barrel, I use anti seize grease on the barrel nut, barrel and receiver threads. I then assemble it, a little above snug. Not very scientific...But I try to remember what the torque was when I took off the original barrel and when setting the new one go just a little less than was set at the factory. Over torque the nut and you can distort the barrel/receiver and it makes it harder to take off the next time. To change barrels, a barrel nut wrench is a necessity. A good bench vise is nice to have as is an action wrench. I have a barrel vise, but a good bench vise will work. I have done several barrel switches including a Remington 700 and those tools sure make the job go easier, but Like I said you can get by with just the barrel nut wrench, padded bench vise and some kind of home made action wrench. The vise just hold the whole assemble in a position to make it easier to work on. The real action is between the nut and receiver. You just work one against the other.