Fires are a big deal.
I get it,maybe you can't imagine a steel bearing bullet can cause a fire.Some folks have already learned the hard way steel bullets can and do cause fires.
This was not exactly a steel bullet.It was copper/lead.A Nosler,I think,from a 7mm Rem Mag.
I use a couple of rebar pickle forks for target stand uprights.Ipound them in,and stuff a piece of black cello-tex siding in the fork.I staple my targets to the cello-tex.
I was sighting in at 300 yds and my windage was a bit off. I clipped the rebar.
I thought I saw a whisp of smoke from my target. Nah,couldn't be.
Then,"By golly,that IS smoke."
By the time I jumped in the pickup and got to the target with a GatorAde fire extinguisher,I had flames.
This was rolling grassland/sage on a private ranch a long way from help. A good breeze was blowing. Dry sage burns like is been sprayed with kerosene.
That made a believer of me.Copper bullet,but the steel spall from the rebar lit it up.
Folks have been starting fires by striking steel to a rock for a long time.
The range is making a legit call.
FWIW,here in Colorado,between the danger of stray bullets and fires,Roosevelt and Arapaho National Forest sport shooting is in the process of being severely restricted or eliminated.