I tried the same thing and couldn't replicate it. Not to say that it can't happen. Mine was snug to one side of the barrel, which was annoying, so I sanded it. That's definitely not the first time I've had to do some trimming to float a barrel, so I dismissed it as a minor annoyance. As far...
My suggestion is tighten the action screws to the point that you think the plastic is going to break...
I had to do that with my 6.5 and I had been pretty timid about screw torque, but once I snugged them down my groups shrank considerably.
The new 6mm MAX is also intriguing if you want to stay with the same bolt face. I really like the 6 ARC and will probably get a 22 ARC, but the 6mm MAX seems to also be a decent contender. However, I don't know what the logistics look like of getting any of that ammo or components up to Canada.
Color me skeptical. They haven't put much focus on anything with an M77 action in a couple years. But if they do, then cool! One of my favorite rifles is an 18" stainless model that I put in their synthetic stock. It's probably the most utilitarian rifle I own, and a pleasure to shoot and carry.
I'm a sucker for the Bell and Carlson sporter on my 6ARC. They make an M40 style too. I'd also consider a JTAC or Stocky's. The JTAC would look sweet with that heavy barrel.
1/2x20 would be one of the only potential deal breakers for me. But I suppose that it would be relatively easy to get it chopped to 18-19" and threaded 1/2x28. I'm currently dealing with that on a gun I purchased on a whim (Voere S16 .223) and I'm debating whether to get a 1/2-28 adapter or...
It's been stated repeatedly that the OTM bullets, specifically Sierras, are inconsistent in their upset. They might be devastating, or they might pencil through. If that's all you have, maybe aim for neck or shoulder to increase the chances of frag/upset or at least immobilization.