ApacheCoTodd said:
"'cause I want to and it's legal."
That is probably the worst answer you could give anyone. When you say something like that the first thing that comes into people's minds is that it being legal needs to change. In fact someone not even thinking in terms of legal and illegal but just not approving of an activity is suddenly thinking in terms of legality in putting a stop to the activity.
You just focused their attention on the way they actually can impact you.
Turning someone that probably wouldn't have been a threat to your ability to do that activity into someone that may well be part of why you won't be able to do it in the future.
You are essentially organizing your own opposition into people thinking in terms of legislatively changing your ability to do that activity with restrictions or laws, rather than just disapproving or not understanding the activity.
Rather commenting that people don't need to camp either demonstrates that people doing things is what causes risk, and for there to be no risk you would have to have people not doing anything unnecessary, like camping, shooting, etc.
Hot bullets after impacting a surface can cause fires. It is rare but when metal is rapidly deformed a lot of heat is generated, and if it then lands in the perfect spot the high temperature can cause ignition.
It is rare, but when you have enough people doing an activity, the round count adds up and rare happens.
The best way to avoid it is to shoot in places without fuel, and into a backstop. If there is small amounts of fuel at the backstop one needs to insure there is enough clearance around it that it would not spread.
Now steel ammo, and even shooting steel objects (not purpose made steel targets generally) thin enough to punch holes in with regular ammo sends pieces of metal with a high propensity to spark when it strikes hard surfaces and rocks. This cause of ignition is more common because rather than relying on the bullet to be hot enough to cause ignition on vegetation it lands on, it instead just relies on a spark to begin the fire, and so the high temperatures of auto-ignition are not needed.
Steel ammo is the most obvious source, but shooting at hard steel or metal objects that you can punch holes in amounts to something similar. It still results in pieces of steel flying away from the target at high speeds.
Shooters shooting at appliances, and other junk (computer components for example) with thin metal pieces can certainly cause fires if not done in a safe spot.
(Although the trash some leave behind is more likely to result in shooting restrictions than fires are.)
Sparks from hard metal impacting rocks is not rare, and while most bullets are not made of such material many pieces of hard trash targets that will fly off at high velocity are.
In fact you can get it to happen every time if you get the angle right.
I remember shooting BBs primarily made of iron/steel from a BB gun at night on flat cement in a safe area (they will all ricochet and may be dangerous) and every single one would spark within the right angle, creating quite a visible demonstration from even a low velocity and mass projectile.
Obviously something of greater mass and velocity will cause even more particles of metal to fly off as sparks. Showering something in sparks that is dry and thin can easily lead to a fire.
It is a concern beyond just target shooters:
I bet steel shot from shotguns for example creates a bunch of sparks when they impact rocks at much higher velocities than a cheap bb gun created (though not likely visible in daylight hunting.)
I can just imagine the shower of sparks shooting cement at an angle with steel shot would create.