I have an urge for a 6mm Remington long-range rifle. I plan to get a 1 in 9" twist from Pac-Nor. Their barrels are 26" long. I will be putingt it on a Stevens model 200 that I have in .243. I am wondering if it would be best to trade the .243 for a long action.
Also, I want to be able to carry it around so I'm wondering what barrel contour would be the best compromise between accuracy and carrying ability.
Right now, I'll be scoping it with an old Weaver V-12.
What I'm aiming for is a rifle that will be "pie-plate" accurate out to 600 yards.
How can I improve on this ?

<<<Their barrels are 26" long.>>

Just to be clear, you can have the barrel made shorter if you want. I'd go with a 24" barrel on a 6mm Remington, especially if you plan on carrying it around.

Regarding short action vs. long action, I think I would stay with the 243 chambering if you plan on keeping a action limited to a 2.8" magazine. Unless you have the room to seat out the bullet on a 6mm, you essentially have the same thing as a 243. The 6mm needs a little room to optimize the cartridge.

Use a 1 in 8 twist for long range