I tooled up to reload 223 this past summer. I've done most of the steps experimentally but have not started to load in earnest. I needed to put that project on pause when school started, and then hunting season, and other projects. I've yet to acquire the primers (I have 1 or 2 boxes), the brass, and my powder of choice (I have a few pounds of H335 but I'll likely use something else).
For me the reason to reload 223 is to have the best loads I can make for a Mini-14, and because I enjoy hand loading. If I had an accurate bolt-action in 223, I would certainly reload for that. Reloading for a Mini-14 might be a bit suspect then, considering they're known for their inaccuracy. I'm hoping that is a bit of stigma left over from the Mini's earlier pencil-barrel design and a bit of myth and exaggeration. My Mini has not demonstrated bad accuracy yet, but I haven't worked with it enough to determine just how accurate it is. I don't intend it to be scoped (except for load development) or to hit small targets at many hundreds of yards. So why reload?
I believe I can save money, but not for the cheap 55 gr. FMJ ammo. Factory 223 with high-performance expanding bullets like Barnes TTSX, Hornady CX, Nosler E-tip, is expensive. If these components can be sourced inexpensively as seconds, they can be loaded into cartridges at significant savings provided sufficient scale (thousands of rounds). The savings in reloading 223 isn't in the NATO-spec overruns, but in the special-purpose cartridges for varmints, hunting, etc.
Saving money loading high-performance cartridges can't be done with mixed headstamp range scrounge brass, nor can it easily be done with new Lapua cases. I've got to find a source of quality, same headstamp fired brass that isn't damaged. My initial plan was to shoot my own supply of LC brass, but having procured enough cartridges, I decided to keep them instead of shooting them. Now I think I've found a source for what I want, but I haven't acquired it yet.
I also need to acquire those SR primers as mentioned. It's a pity I didn't get them when they were 7.9 cents a few months ago. On the other hand, since loaded 556 has also gone way up in price just in the last couple months, reloading could be a better proposition. Doing it to save depends on buying components when they're priced low. It might take years to find the components at good prices, but some of them like primers and bullets aren't specific to one cartridge, so it could be worth it to stock up when they're cheap.