Rifle usage in Edgar Rice Burroughs Barsoom

There are remarkably few mentions of the rifles being used, and as far as I know none that feature the extreme range. In A Princess of Mars John Carter is attacked by Tharl warriors sent to capture Dejah Thoris:

There was but one slight chance and that we must take quickly. Raising my strange Martian rifle to my shoulder I sighted and touched the button which controlled the trigger; there was a sharp explosion as the missile reached its goal, and the charging chieftain pitched backward from his flying mount.

In Thuvia Maid of Mars Thar Ban abducts Thuvia then is pursued by a group who also wanted to abduct Thuvia and were ticked off that Thar Ban got in first:

Now from behind her came the shouts of her red abductors. They were racing madly after him who dared to steal what they already had stolen. As Thar Ban reached the side of his mount he snatched his long radium rifle from its boot, and, wheeling, poured three shots into the oncoming red men. Such is the uncanny marksmanship of these Martian savages that three red warriors dropped in their tracks as three projectiles exploded in their vitals.

Later in the book Jav relates to Cathoris how Lothar was attacked by Torquasians, and rifles are mentioned but it isn't clear if they are the same rifle:

"But after the Torquasians had retreated beyond bowshot, they turned upon us with their terrible rifles, and by constant popping at us made life miserable within our walls."

And later Cathoris' flyer is attacked with rifle fire. Again it isn't explicit that these are the Martian long rifles:

Then Thuria came low above the other craft. The Kaolians were forming under their officers in readiness to board, and then a sudden fierce fusillade from the rifles of the green warriors vomited their hail of death and destruction into the side of the brave flier.

In the seventh book, A Fighting Man Of Mars, a new type of rifle is invented that shoots a disintegrating ray rather than an explosive shell.

I suspect that Burroughs was indulging in his usual purple prose when initially describing the rifles, and not introducing any important plot device. How would you aim a rifle at a target 200 miles away? Especially when the horizon on Mars is only a couple of miles away.