I have bore-sighted hundreds of rifle. When I first got serious about rifles I had a shop where I could put a rifle in a vise, then aim at the tip of my neighbor's roof, and come very close.
In fact I once bore-sighted a .270 of mine just before hunting season. When my father-in-law showed up unexpectedly wanting to hunt, on a day when I had to work, I handed him the rifle and box of 130-grain ammo and told him to shoot it at a box to see if it was close. Of course he didn't--but did shoot a deer and was puzzled about why I'd made the suggestion.
I find collimators (which I've used for 30+ years) very useful for a number of other tasks, including testing adjustments and how much variation from point-of-impact there might be when as variable is turned from minimum to max. Yeah, you can find that out by shooting--and burn up a bunch of ammo.
Plus, neither bores-sighting or a collimator is perfect. I have tested both on a number of sighted-in rifles, and results vary considerably, mostly due to barrel thickness and bedding of the stock's forend.
