Re: Rifle cleaning question.
Pby5cat,
I have an AR15. The bore guide I use is the Gunslick bore guide. My rod fits a bit loose, so I also use one of those cone shaped muzzle protector things to center it in bore guide.
Grey,
No offense taken at all. That's an excellent question, and one I'm sure others can answer more accurately than I can. I'll give it my best shot, though. The damage done is generally on the throat and muzzle crown. The argument of soft materials not being able to harm hard materials is misleading and misunderstood. It is true that a brass cannot scratch hardened steel, however, brass can still cause deformations to steel. Denting/deforming is determined by stress (Force/Area), not hardness. If you want to see an extreme case of this, take a sharp knife blade and press the edge sideways on a brass rod. Many knives, especially cheaper ones, will hold a permanent deformation with little force. With enough force, even the best steels will deform.
A similar thing can happen on the throat and rifling (think impact damage). If the rod is inserted crooked (ie. no bore guide) it can contact the rifling near the chamber and cause dings (excuse the scientific lingo...). A ding in the throat can be enough to cause accuracy problems. The rod can also bow and do the same thing to the rifling near the middle of the barrel. This is bad, but won't have as much of an effect as a damaged throat.
Although this has little to do with a bore guide, many people have messed up the crowns on their rifles with brass rods and jags, as well. That thin corner on the muzzle is a stress point, as is the edge of your rifling. When impacted hard enough, it can and will accept a plastic deformation. I use brass jags exclusively, and have dinged the crown on my .22 rifle more than once by not paying attention when pulling my rod back through the muzzle.
It should also be noted that soft metal rods and nylon coated rods will pick up abrasives very easily. When the rod contacts the bore, it will abrade it unevenly. Unevenly is, in my mind, the key word here, and what separates this from what happens when you fire a copper bullet.
I'm not saying you couldn't get away with using no bore guide, but I don't feel saving $30 is worth risking a $450 barrel. Even if the bore guide only makes the barrel last 20% longer, that still saves you over $100 in barrel life.