During the first Indian attack the three trappers are firing single-shot muskets, which must be reloaded with powder and ball after each shot, but they are seen in several shots firing repeatedly at the Indians without reloading.
Although the story takes place in California in the 1840s, and an effort was made to have American and Mexican soldiers wear the appropriate uniforms of the time, the civilians are wearing the familiar Stetson-type cowboy hats, vests, boots and other clothing that can be seen in any western set in the 1880s-1890s Southwest, which weren't worn in the California of the 1840s.
The leather sling shown on the rifles were the M1907 military sling authorized in 1907. They are still used today.