[quote=Nallore]
Yes, Halo 4 weapons were most likely prototypes at that time, except for maybe the Halo 4 assault rifle the pistol, DMR, BR and the SAW if you look hard enough in the second level of Halo 4 there is one those weapons were on the Dawn.
[/quote]
The wiki says the MA5D was standard issue post-war, the BR85HB SR and M395 were used post-war. I'd expect the M45D to be the same. The M6H pistol was standard-issue five years after the RP. Wouldn't expect any of those to be in use in '50, and in great numbers if at all.