I swapped barrels on my .243 a while back, and didn't notice the scope cover was touching the new barrel whereas it had clearance on the old one. POI shifted some 8" I think, though it was still shooting good groups. Took me a while to figure out what had gone wrong.

Back in the UK, using a moderator on my centrefires, if it wasn't tightly screwed onto the barrel, POI shited and groups went to hell. With it fitted properly, there was still a POI shift compared to shooting without it, but the groups were just as tight.

I would never hang a torch off the barrel - I either use a scope mount for the Lightforce, or hang it off a piece of rail attached to the underside of the stock on my .204, put there for that purpose.