My friend sold his home and moved to Phoenix a few years ago. He had a hard enough time transferring a hundred or so guns (it seemed like that amount) to the mainland so he asked me to help him out with his ammo.
I ended up buying something like 30K cartridges (a lot of .22s but more centerfire rounds by far), 50K primers and about 40 lbs of powder.
I've sold off a lot of that through the local gun shows and our local forum but I still had enough to where I recently sold some .308 and 5.56 at a tidy profit.
Just before the pandemic became serious I managed to pick up nearly 2K .38 rounds, 3K 9mm and 1+K of .308 and M2 Ball. The timing was perfect--I had cash and people I knew or just met had ammo they wanted to get rid of. I've yet to make a decision about selling some 9mm, the .38s I'm keeping to feed my new Smiths.
I probably have enough cartridges to last me 10 to 15 years but the thing is this--I decided long ago to be prepared to buy entire collections, accumulations, estates, whatever, with the goal of flipping most of it to fund other buyouts. I enjoy doing it, I know my local market very well and I treat people fairly and I deal honestly. I have repeat business from some guys, I get referrals from others and most of all I help people who sometimes get stuck with more stuff than they know what to do with.
I have fun doing it, I've picked up some very nice keepers along the way and I've managed to help more than a few people with their problems.
I don't resent the term "opportunist," I'm more of a problem solver.