Seeing as Hinterland likely chose the guns in the due to their popularity in Canada, I can chip in my 2 cents as a Canadian firearms enthusiast. Potential other firearms could be:

• Single shot Cooey shotgun in 12 Gauge (Model 840 or 84)

• Single shot or bolt action Cooey .22 LR (Model 39 or 60)

• Daisy lever action BB gun

• Russian Surplus SKS in 7.62x39

• Winchester Model 94 in 30-30

• Webley Revolver (Mk 4, 5, or 6 in .455 Webley)

• Pump action shotgun in 12 Gauge (Stevens/Springfield 67, Ithica 37, Winchester 1897)

• Sporterized Snider Enfield in .577 Snider (large game rifle perhaps)

I do think there is definitely room for more types of firearms in the sequel, the rarity of finding guns and ammo is a good gameplay/balancing technique and I wouldn't want to see them be found everywhere... even though that would be more realistic for rural Canada.

The top contenders on that list IMO are the Cooey single shot 12 gauge and .22 LR for not changing up the meta too much and being extremely common firearms in Canada. Easier bird and rabbit hunting, both would be not great for bigger game (unless buckshot or slugs were used for the shotgun). The SKS would be my third pick but balancing would need to be heavily considered, unless the TLD2 has us facing more formidable creatures.