Red Dead Redemption 2

There are some sweet secret guns in RDR2, and here's how to get your grimy mitts on all of them!

Complete the following tasks (listed in alphabetical order) to get these guns:

Algernon's Revolver: Complete the "Duchesses And Other Animals" mission, then speak with Algernon Wasp at his shop in Saint Denis. 
Calloway's Revolver: You get the gun from Slim Grant, but in order to meet him, you'll need to talk to the writer in the saloon in Valentine. He will send you on "The Noblest Of Men, And A Woman" mission, where you'll need to take down 5 gunfighters. You can talk to the Sheriff in Annesburg in Chapters 4-6 to get Slim Grant's whereabouts. 
Flaco's Revolver: Get this gat through undertaking another of the duelist missions, this one against Flaco Hernandez. Talk to the writer in the saloon in Valentine, who will send you on "The Noblest Of Men, And A Woman" mission. Flaco is in his camp, located near Cairn Lake, outside Colter.
Granger's Revolver: Emmet Granger gives up this steel, after you talk to the writer in the saloon in Valentine.He'll send you on "The Noblest Of Men, And A Woman" Stranger mission; you can find Emmet Granger at the homestead east of Flatneck Station.
Micah's Revolver: Go back to Micah's camp on Mount Hagen after completing Epilogue 2. Pilfer Micah's gun off his corpse at the site of the final shootout in "American Venom".
Midnight Pistol: Get this from Billy Midnight, after talking to the writer in the saloon in Valentine on the "The Noblest Of Men, And A Woman" mission. Billy Midnight is one of them can be located at the train station in Rhodes.
Otis Miller's Revolver: This beauty is found in a hidden treasure chest, in a little cave north of Cholla Springs. Head towards the northern mountains, staying west of Twin Rocks in New Austin, but you can't do anything without the two treasure hunt maps, one of which is found in the Hermit Woman's shack, east of the Little Creek River in West Elizabeth and the second located in Manito Glade cabin, just north of Annesburg. 
Rare Rolling Block Rifle: At the end of the "Magicians For Sport" mission. head up to where the sniper was and grab it.
Rare Shotgun: The Hermit is packing this bad Larry, and can be found in a cave, west of the Hanging Dog Ranch. You can talk to him 5 times, with a three day break in between discussions, or just light him up and he'll drop it.