guntech and WF give you good information. Model 7 rifles often have thin pencil barrels, which are not conducive to good accuracy.
Some shooters get lucky, and find a load that works very well, some don't and at best the rifles shoot in a mediocre manner.
If you're going to this much expense and effort, do it right the first time, buy a reamer and if possible, get a set of dies made up for that reamer. I don't know if the reamer makers still offer that service or not, but you can send that reamer to Redding or whomever you choose and they will make up a set of dies to match your rifle's new chamber.
As for rifle barrel contours, especially with your cartridge of choice, I would go with a No3 contour for rigidity and have it fluted to remove weight and aid in cooling if you're going to shoot long strings.
Then, you want to make sure the barrel has been properly heat treated so it won't change points of impact as it warms up, over a ten shot string.
If you don't want to go to the expense of heat treating as a precaution, then you're relegated to shooting until your barrel is almost uncomfortable to grasp with your palm after shooting and allow it to cool back to ambient temperature or cool it down some other way.
guntech suggests a 22 in barrel, most likely to wring as much velocity out of the barrel as possible, while still maintaining rigidity, good call.
I would likely have such a barrel finished at 20 inches to reduce weight and maintain rigidity for best accuracy. The advantage of this is the ability to shoot heavier bullets a bit faster.
You don't say which bullet weights you want to shoot.
Many people like a 1-12 twist rate if they're going to shoot 165 grain bullets or less and that usually works very well. Some folks say their 180grain bullets shoot extremely well with this twist rate. It may be luck of the draw or the bullet design they're shooting. I don't know if long for weight monometal bullets will shoot well with this twist rate. Maybe someone else has tried them, such as trevj?
1-10 was deduced well over a decade back to successfully stabilize 220 grain bullets at velocities around 2300 fps. The bullets of that weight were all flat based, round nose design. Monometal bullets will be much longer for any given weight than conventional lead core offerings, even some of the ELD types. So, you may want to consider a faster twist rate as you suggested a 1-9 or even a 1-8 if you're going to try shooting the heaviest 30 cal. monometal types available and designed for long range shooting.
RJ
