I was just wiping down a new, and so far
unfired, Colt Carbine and I noticed something
worrysome.  There was no oil in bore and I can
see what appears to be very slight corrosion
in the rifling when looking into the muzzle.

Could this possibly be copper fouling from the
test firing?  How many rounds before Cu fouling
is visible?  If it is corrosion should I
worry?  I always store firearms with a lightly
oiled bore, so should I just oil it and wait
until I make it to the range?

Thanks.

J

If the orange colored stuff is only on the lands, not the groove of the bore, it is most likely copper fowling.  Corrosion will have a rougher look to it and sort of look like it is growing on the bore, whereas copper fowling will be flatter and smoother looking.  If this is a chrome lined bore, it is copper fowling.

On a new barrel, firing just one round can leave copper visible on the lands of the bore.  Not seeing the rifle, my guess would be that it is copper fowling not rust, so just clean the barrel with good copper solvent and then leave a thin film of oil.  Just thought of one other way you could tell if it is copper fowling or rust, clean the bore with CLP only, if you can still see the orange colored stuff it is copper, if you can't then it probably was corrosion.  

If it was corrosion, don't freak out, just clean the bore real well with CLP and leave it oiled.  The CLP should remove most if not all of the oxide and keep it from reforming, and I would greatly doubt it would affect accuracy at all.  The bore would have to be completely crusted over with corrosion before you would see any degradation in accuracy.

It probably doesn't have a chrome lined bore since it's a new Colt.  It could be a little rust but don't worry about it.  The AR(even without a chrome bore) is designed for an enormous amount of abuse.  I would clean it like you normally clean a rifle barrel and don't worry about it.  

I’d run a patch with CLP on it down the bore and see what comes out.

If that doesn’t do it, then try a bronze bore brush and a copper removing solvent, followed by a few patches.

Dry patch the bore between these steps to keep the different fluids from mixing.  Also, when you’re finished you should clean the solvent out of the bore brush since otherwise it will eat the brush bristles over time.

I suspect this will solve your problem.

If it’s still under warranty and turns out to have a corroded barrel, it needs to go back to Colt!!

While a corroded barrel can usually shoot well when clean, it will also foul pretty quickly with a loss of accuracy (until it’s cleaned again).

Well I tried using CLP on a patch and got nothing.  I then tried Cu cleaner and got a whole lot of residue.  I was really suprised that one round for the test fire left so much Cu.  Anyway it's clean now [:)]

So thanks to all for the advice!

J

I just love a happy ending!!!!