After the Civil War, the army had a huge surplus of model 1861 style muskets that were now considered to be obsolete. Breech loading cartridge style weapons had proven to have a much faster rate of fire during the war. A guy at Springfield Armory named Erskine S. Allin figured out a way to take the old fashioned muzzle loading musket and very cheaply convert it into a breech loading cartridge style rifle. This conversion cost about one fourth of the cost of making a new rifle, so it was a very popular idea at the time. These rifles were called “trap door” Springfields because of how the breech mechanism worked.
In the 1870s and 1880s they stopped just converting old rifle-muskets and started making rifles from scratch. They also standardized on smaller calibers, making the old trap door Springfields obsolete. The trap door Springfields were then sold off to civilian gun suppliers, who often chopped off the end and modified the stock to shorten them into hunting rifles. These would have been cheap and easily obtainable in the late 1880s and early 1890s. Trap door Springfields are single shot rifles firing .58 caliber rim fire cartridges.
Rifles like the Krag-Jorgensen repeating rifle had been around since the mid 1880s but I’m not sure how easily obtainable they were for civilians. Variants of this rifle started to be used by the military in the mid 1890s. The U.S. Army adopted a variant of this rifle in 1892, which caused them to dump even more of the trap door Springfields onto the market right around the time of your scientific expedition.
The Winchester model 1894. one of the most popular rifles in history, would have been brand new and probably would have been carried by a lot of hunters. Other lever action Winchester rifles would have been common as well. These are the typical rifles you see in cowboy movies. Remington had started in the typewriter business, but in the late 1880s had gotten into the rifle business as well, just in time for your scientific expedition.
There were a lot of other single shot rifles around. These typically had a range of a few hundred yards, which compares pretty favorably to modern rifles. What they lacked compared to a modern rifle is rate of fire. A single shot rifle typically can fire about 10 to 12 rounds per minute.
Pistols and shotguns were certainly available. Like rifles, shotguns had also progressed from being muzzle loaders to using modern style cartridges. Pistols had also recently moved away from using percussion caps to using integrated cartridges. The Colt Peacemaker was pretty typical of the types of pistols that someone in the 1890s would have been carrying. It’s your basic typical cowboy style revolver. Smith and Wesson pistols were also popular. Pistols then, as now, were only accurate to about 50 yards due to their short barrels.
Grenades in some form or another have been used for over a thousand years, so they wouldn’t exactly have been a modern invention in 1895. I doubt that a scientific expedition would carry them though.
Safeties had been around in one form or another for hundreds of years. Early safeties were “dog locks” which were basically little catches (dogs) that latched onto the lock mechanism and prevented it from moving. Marin le Bourgeoys’ original flintlock rifle design (which became the standard for the next 200 years) had a “half cocked” position from which the flintlock could be loaded but not fired. If you’ve ever heard the phrase “don’t go off half cocked” this is where it came from. Single shot cartridge rifles sometimes had safeties and sometimes not. Any rifle back then, if left loaded and ready, could be fired by a child or an animal or just by being knocked over if the trigger happened to hit something on the way down.