I have probably fired more tracer than will fit in a 5 ton truck. Seriously.
Really no harm to barrel. Hazard is the round has a tail of VERY hot flame about 12" long behind the bullet in flight. If it hits something combustible before the tracer has burned out, (like the Earth, maybe) you have a good chance of setting it on fire. We have burned off more ranges with M60s and Ma Deuces than you would believe!
However, as a member of Armed Forces, was not my land, and not my worry. There was a firebreak plowed around the impact area. Designed to burn. We would use artillery simulators to blow out some fires close to us.
YOU- on the other hand, are likely a private citizen. And while I am NOT a lawyer, I'll bet you a beer and a steak that YOU have a law on the books in your state- and that it says something on the order of "start a fire, pay for damage from the fire AND cost of putting it out."
Say, did you ever watch the videos where they use helicopters to drop water on forest fires? Did you know those cost about $650 an hour to operate?