Ok, so my first post here but I'm a long time lurker of the forum. I also would like to add that I have a very great grasp and knowledge of the zombies storyline and the involvement of the vril-ya, illuminati, The flesh, G935, and other organizations. Sorry if anything like this has been posted before.
On to my theory that explains many time anomalies and why guns are cannon!
So in Die Rise's starting cutscene we hear a mysterious voice tell Samuel that he needs to "mend the rift". Now my theory is that this "rift" is a rift in time and space from to much teleportation from the OG crew which is causing different time periods and era's to mix together.
This is very much seen in BO2 and started since the first time Dr. Richtofen overloaded the teleporter in Der Reise with the Wunderwaffe DG-2 sending them to Kino Der Toten. In Kino we see the MP40, a weapon very much used I'm WW2 and the 40's but obsolete by this time. Kino also has many Nazi memorabilia left behind as flags and the teleporters. The 40's is clashing with the 60's and fusing into one!
Now in BO2 we see this very clearly with Green Runs old style 60's look yet the futuristic T.E.D.D., Marlton's watch, and the 2025 era weapons along with some 60's era weaponry in the box (FN FAL, Galil).
Also in Nuketown we have the 2025 and 60's era weapons in the box, Marlton in the shelter, The horn from the bus on TranZit all 2025 events and at the same time we have the events from Moon in the 60's going on as well when Richtofen in just taking control.
I'm sure many of you are connecting other links with the other BO1 maps and Die Rise that show this theory to be even more truthful. I also feel this will help explain Mob of the Dead quite well.
Also in BO2 zombies we have the FAL back. Treyarch very well could have used the updated 2025 version but they kept the 60's version in. I think they did this not just for nostalgia from BO1 but to show that the era's are melding together.