First time Bushy M4A3 owner, I have a question on the exterior finish, being the flat black finish, I am surprised how easily it gets scratched up. I'm use to a Glock's tenifer finish. I know it's a gun, not a museum masterpiece, but is there worries about advanced corrosion or anything else, especially the exterior part of the barrel?

Thanks

You dont have a thing to worry about concerning the exterior of your rifle.  I would say that you are going to get car rash when transporting your rifle & some scratches using it.  The heart of your rifle is the reciever & inner barrel.  By the way your barrell in chrome lined so it can take a beating. If they show signs of corrosion you will see an impact.   I am sure you have seen pictures of military rifles which have shiny spots from the abuse they recieve.  No worries,  Chances are you will never have to crawl on the ground with your rifle like the military does.  I know my rifle is in perfect shape,  just have to get that one "dammit scrath" over with and start treating it like it was means to be treated...  Have fun with your rifle,  you made a good choice I might add...

Prosise  

It just needs a nice coat of CLP.[;)]

Im waiting for the day when I have more scratches than finish.  Im 1/3 there.

Had a guy once try to tell me that the condition of his rifle, mostly shades of gray, black and bare metal, was a new finish called "MECHamo" -- for use in highly industrialized and automated environments...

Needless to say, given the likelyhood of deploying inside a robot, he got the can of Krylon, flat black, Bar-B-Q paint (good stuff).

Unless firing a lot of full auto, a barrel should last quite a long time.  And if it was me, by the time the barrel is worn out, it is time to junk the upper receiver, too.  While we are at it, a new bolt is in order with the new barrel.  

I would reuse the bolt carrier itself.