Powders? Stock enough of a selection that a reloader could try three or four powders from Alliant, four from Accurate, IMR/Hogdon, Winchester, etc.
Same with bullets: You are going to need a variety in each type and weight to get a SERIOUS customer's attention.
Primers - - some of everything, to meet the needs of a diverse and educated clientelle.
Hey, shot and wads - there's room for a whole shelf just in wads alone.
REMEMBER -- reloaders are experimenters as well as being people who like to craft their own loads for specific purposes in addition to seeking greater economies for their shooting dollars.
If you were the only store in the area, and I drove 150 miles just to get there (mention,later of the drive home) and you did not have anything near what I needed (or even was curious about) and this happened when I drove back two weeks later, you probably woldn't see me too often.
The internet would get my business - because somewere, the web DOES have exactly what I'm looking for, and FedEx will deliver it tomorrow, anyway. All for cheaper than the gas to drive home (don't forget, that If I drive 150 miles anywhere, I take my wife and maybe another couple of shooters along, and that means lunch on the way up, dnner on the way home - an all-day excursion) from a really cool store that has a lot of high-dollar advertising, and sells their own caps and tee-shirts with their very own logo scren-printed in three vivid colors --- but can't meet MY particular needs when I want.
No matter how grand a selection you might have on fishing gear and what bargains you have on trolling motors, if I come to your relaoding department and you don't/won't stock it, and if I visit twice and you don't show any inclination to meet MY particular wants/needs, then likelihood of my shopping there again is reduced to an infinitesmal minimum.
Just my two cents that I'm shopping with - - - [RANT-MODE = off]
Flash