The Lake City Ammunition plant is only a couple of miles from me. Lake City has a current capacity of 1.6 Billion rounds per year, and supplies 99% of the Army's small arms (through .50 cal) ammunition. See web link.
Army Sustainment: Small-Arms Ammunition Production and Acquisition: Too Many Eggs in One Basket?
I assume this does not include the other branches of the military, but being it is the Army, I would GUESS that this might equate to 1/2 of the ammunition used by the combined military branches per year. Somewhere around 3.2 billion rounds.
So a total production of a billion rounds per week times 52 weeks less the military's use of 3.2 billion rounds = 48.8 billion rounds for the other Goverment departments, LEO, exports and civilian use.
On the surface, that seems like there should be plenty to go around. What percentage of the population are active / prolific consumers of ammunition? What is the percentage of casual shooters or non shooters "stocking up" a few cases. Many many variables here.
I enjoy playing around with the numbers. Nothing scientific, just putting things into perspective. I purposely have left my numbers out, in case someone wants to play to...,but, you throw in guys who blast off 10k rounds per year.....some people hoarding a few thousand rounds...I can see why there is a shortage even with 52 bil annually produced.
I wonder how many rounds us civilians have stored....for the zombies or the ???