I believe that ruining the crown should basically be a non-issue ,as just about all cleaning processes should be performed from the chamber end of a rifle. Just don' t let the cleaning jag slip outside the bore and then try to pull it back thru.......that could damage the crown.
I read somewhere that most good shooters don' t like " bore-guides" either as they believe that they create a specific wear pattern on the crown as well.
I think one of the only things that should be done from the crown end is the initial polishing of a NIB gun as part of the break in process, and is best done with a solid 1 piece cleaning rod. I just did my new Ruger 77 last week and was SUPER careful around the crown area. After all the work polishing and breaking in at the range the last 4 shots were cutting one ragged cloverleaf hole (About .50" ) without any " serious" effort and resting the barrel as I was not sighting it in but rather putting a few miles on the barrel breaking it in.
I think it' s gonna be a heck of a shooter!