Congrats to you on your stockpile! It gives you a warm fuzzy feeling to know you are self-sufficient for ammo production.
Here is how I look at my situation, using your stocks as an example.
400 cases = 2,000 rounds of ammo, assuming 5 loadings per case (this is just a swag average to use for bottle-necked rifle cases, ymmv).
So for the 375, you need of course 2,000 bullets and 2,000 primers, and 23 pounds of powder (assuming all full-power loads). I have been using the 375 myself for about 25 years off an on, and have only loaded about 1,200 rounds, so this would be a lifetime supply for me, for that cartridge! I currently have 800 jacketed .375 bullets, plus a mold. So at my age, I am probably set.
BUT - you also have the wildcard....a bullet mold! So your bullet needs can be reduced, replaced with lead alloy needs (and gas checks, if you use them; and bullet lube). You also need a way to size the bullets if they are not tumble lube type bullets. And your overall powder needs are reduced, but you need a second powder such as RE7 or SR4759 for the mid-range cast loads.
You might also need to up the primer/powder stash now, as careful cast bullet loading can extend the life of your brass (careless cast bullet loading will reduce the life of your brass, through excessive flaring of the case mouths to accept the cast bullets without shaving the lead).
Good on you for working toward self-sufficiency in ammo. The last 6 years should be teaching everyone (in America at least) that the "good old days" may be a distant memory only!
Tim
