I watched the movie Hidalgo when it was first released to the movie theaters back then. Watched it 2-3 more times later on. Was a good movie.
The gun that was fired (or pretended to fire - Hollywood you know) is an original Algerian musket. This style of long gun was unique to this Region. They can be found plain to highly decorated, and all points in between., in a variety of different ways. Even though the guns were decorated depending on the customer's requirements and what he could afford, the guns were built following a long used general pattern.
The forearm of the stock looks like they were shortened. But they were actually built this way. A sort of 3/4 length stock. Every one I've seen is built this way. They used a ball-style trigger, and no trigger guard.
The barrels on almost all are tapered octagon with no swell at the muzzle. The barrels were high quality imports from Europe with thick breeches and a dramatic taper to the muzzle. They are all smooth bore and usually run about 60-65 caliber.
The locks are a strange looking hybrid of sorts. Many of the general characteristics of the lock copy the very earliest Spanish miquelet locks. Post wheellock period. They all have a dog-style safety latch at the rear of the lock plate. Historically, the Spanish locks operated from the heel of the hammer, pushing DOWN on the mainspring. But these Algerian locks operate from the toe of the hammer, similar to Italian (Roman) style locks, pushing UP on the mainspring. Interestingly, these locks are both signed and dated on the bottom of the mainspring area. The mainsprings are very strong and chew up flints quickly. LOL
I own two of these Algerian muskets. Here's some pics of the first. It's decorated with lots of ivory/bone inlays and 5 silver barrel bands. It's .60 caliber smooth bore. An inspection of the bore shows no more than a possible test fire. It's likely fully safe to shoot today. But I have another shooter I'll post after, as well as a close up of the lock details.
Rick