Hold on Joel. There are heat treaments that can be done to barrels to stop them from changing point of impact when they get hot. They aren't cheap, and I don't know if anyone in Canada does this treatment, but it is available in the US.
No, I'm not going on about Cryogenics.
A few years ago, when I ordered the last factory profiled barrels from Shilen in the US, one of the options listed on the form was heat treating. I hadn't seen it before, so I called them and asked what it was, and they told me it was a special heat treatment to stop shifting harmonics caused by increased heat during firing long strings at the range, and for Varmint shooters.
I didn't order the treatments because the people paying for the rebarreling, didn't feel they needed the rather expensive option.
WL, your Mod 70Win, FWT barrel did not get this special heat treatment at the factory. To my knowledge it's not a factory option either.
For someone in your line of work, that rifle may not be what you need on the job, especially if you're in a "cull" situation and the shots are fast and close together.
The FWT type rifles are not meant for this type of shooting, and most will not do it well.
Many decades ago, I was involved in a domestic sheep cull. The fellow who owned them went broke, then walked away from the flock, which went wild. Some died in the winter, when their coats froze together, and they were easy pickings for the Coyotes, but most of them survived.
There were close to a hundred animals, in all stages of health.
The realtor, who bought the property at auction, tried to find someone to come in and take the animals.
No takers, mostly because it was a difficult place to get to, and there were concerns about disease.
The animals were a nuisance to the surrounding farms/ranches, so the MOE hired a friend and myself to "reduce" the flock to "0" animals, and remove the carcasses.
It took a four days, because they were no longer tame, and human contact for the past couple of years was not happy experience, and a poor choice on our part for rifles.
The shots were anywhere from 50-300 meters, and usually there would be at least a half dozen animals together.
We both used Rem Mod 7 rifles, chambered for 243Win, with factory, wood stocks, and Leupold 2x7 scopes, shooting handloads.
The cartridge choice was just about perfect for the job, but those pencil barrels were a big negative, and a job that should have taken a day at most, turned into four days of hiking over brushy, steep terrain, because of lack of consistent accuracy after the first couple of shots from each rifle.
The Mod 7s would have been fine for a sporting Deer or Bear hunt, but not for a cull.
Google "John Barsness and heat treating barrels for accuracy"