I think the bear spray is more like 30 feet. I’ve heard where the bear spray is quicker than trying to get an aimed shot off and will scare the bear off (even just the sound and the fog). But sometimes they come back in a few seconds - so then a gun is needed.
I try to carry both, but often it is just the shotgun loaded with Brenneke slugs. So far the bears know we are out there working and stay clear.
It’s been seven years since I’ve been up in the mountains, outside of Canmore and the Banff townsite, so I’ve forgotten the distance for bear spray. Even at 30 feet, there is little time. There are several other things that I forgot to mention about hiking in K-Country and the National Parks. That is to always wear bells, or something that makes noise as you hike. Unless the bear is ravenous or rabid, they want to meet us even less than we want to meet them. Bells give them a warning to clear the area. Dogs, off leash, unless they are bear dogs, are not a good idea. They are more likely to provoke a bear than scare one off.