This video explains how to get Micah's gun before the Epilogue, both in Chapter 1 and 2. Some people have managed to get it even past these mission but these two methods shown here are the easiest ones so far.
NOTE: The first method was actually discoverd by eyezayar!
eyezayar's channel:
/ @eyezayar
eyezayar's video:
• How to make Red Dead 2 an insanely difficu...
Ellemen's channel:
/ @ellemen_lmn
Ellemen's video:
• How To Get Micah’s Revolver Early (Chapter...
Zoka J Z's channel:
/ @zokajz1021
Zoka J Z's video:
• RDR2 MICAH’S REVOLVER EARLY IN GAME CP2 TRICK