I shoot this type of stuff all the time around here . It has to be REALLY dry for it to set fire to the rocks and dirt . We did have a really wet year here a lustrum or two ago , desert greened up real good . One 250 rd belt of '06 tracer fired into the night started 17 seperate fires . Most died out in a few min. , but some lasted a half hour or so. Still , it is the range record .
Chris