Nothing special but nothing bad about the triangular vs. conventional profiled Remington barrels in regards to accuracy.
The Rem triangular barrels aren’t really triangles, but the geometry below will give you an idea of what weight, stiffness, and cooling area look like for comparing triangular prisms to cylinders:
For equal weight, a triangular barrel will be 55% greater diameter than a cylindrical barrel, and the flat side will be ~35% wider than the diameter of the round barrel.
For equal cooling area, the triangular barrel would have to be 21% larger diameter than the cylindrical barrel, which means the flat side would be ~5% wider than the diameter of the round barrel.
Note: this is considering the diameter of the triangle to be a cylinder the triangle could slide inside. The width comparison is really comparing a square tube which the barrels could slide inside - I offered both because the round barrel’s widest point is uniform across its centerline, whereas the triangular barrel’s widest dimension does not pass through the centerline.
What the above means: a round barrel of the same diameter as the triangular barrel will cool FAR better than the triangular barrel, whereas the triangular barrel will weigh less for its level of stiffness.
Since the Remington triangular barrels are rounded at the corners, significantly, the cooling loss isn’t as bad as the math above, but the stiffness gain isn’t as good either.