I have been reading post on here for a while and I have read some that say that guns will not be accurate if you ruin the crown. From what i understand this is the tip of the barrel and can be ruined by bad cleaning rods. I have a dewey coated cleaning rod is this all the precaution i need to take or should i make sure all my bore brushes and everything are made of a certain material. Thanks-Sam

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!

If you clean only from the breech ,use a bore guide and your dewey rod, you should have no problems.You should also never use stainless brushes as they can damage stainless barrels.

If you put something like a block of wood up tight to the muzzle while cleaning to keep your jag from popping out of the barrel, you should never have a problem. Use phospho-bronze brushes only. A bore guide just keept the cleaning rod from rubbing on the throat area of the barrel and keep the solvent and gunk from getting into the magazine. I don' t know how useful thay are as I don' t use them, unless you have a match grade barrel, the throat is going to be less critical than the crown anyway.

So if I have run my bore brush out the end or started it at the muzzle end then have I screwed the pooch or what? What should I do?
My M77 has a hard time holding a 3 inch group at 100 yds. I had racked it up to a scope but I had the same results with 2 different scopes.[X(]

Had the same problem with mine until I did a trigger job, floated the barrel and bedded the action. Now it shoots 1" or less with factory fodder.

How would you do it from the chamber on a semi auto rifle?

If you clean from the muzzle, it is best to use a hard, one-piece steel rod, not one which can carry imbedded abrasive materials, like aluminum or brass rods will.