I know to clean it from the back toward the muzzle I know to never clean it from the muzzle but from what i read damaging the crown or rifiling is still easy to do even when cleaning from the right direction my question is if the ar bore guide necessary or not for cleaning an ar 15 rifle???
Listen.. You can wear down a rock if you just drip water on it for a million years or have a hundred billion people walk on it over centuries. You can wear down a steel crown with a brass rod if you clean your rifle 20 times a day for the rest of your life too.
If you are typical you probably shoot 100-200 per trip and a trip is likely a month between. That means deep cleaning 2-4 times a year for most people. That means it would take approximately 300 years before the crown started to show signs of wear from the cleaning rod, and by that time, the barrel would be worn out in many other ways to go with it.
Its a non issue so long as you are not doing something that defies common sense. If all you are doing is jacking a brush and a cleaning wad down the pipe a few times a year with a brass cleaning rod and doing so only with a gentle pressure applied by your hands without any power tools or hammers or the like, it will be fine, for real. And if you are STILL worried about it, pop one peg out, open the gun, and jack it down the barrel from the rear using the aforementioned wooden dowel rod and a piece of paper towel soaked in cleaning solvent. I promise that the wood & paper won't hurt your gun this eon if it is indeed made of actual metal.
to put it in perspective, you repeatedly force an oversized piece of copper down the barrel at thousands of PSI and moving at thousands of feet / second while setting off an explosion and blasting the thing with hot gas. Nothing you can do with that brass rod should even get CLOSE to this level of abuse ... the cleaning supplies are softer and pushed thru with less force and the rod is smaller in diameter than the bullet.