I'd think GunBroker would be a suitable spot.
It requires making an online account with GunBroker. But prices are sky-high right now, and if you create smaller batches of the stuff I'm sure you'll get good money for the stuff. Say, powder in 8lb jugs or 5-8 1lb batches, even-lot stuff, primers in 2000ct or 5000ct batches. Selling the whole bunch in a single sale is a nice hope, but doubtful any one person would have need for all of that in the combinations you've acquired. So, chunking it up into smaller, similar batches might be a good way to unload it relatively quickly. If wanting to sell it even quicker, set an auction to have a basic minimum "floor" price you'll accept, but as a "no reserve" auction and with a fixed number of days or weeks for the auction. That way, so long as you get the minimum price, it'll be gone at the end of the auction.
Of course, as others have suggested, primers and powder are Hazardous Materials items. There are codes requiring lawful handling of such items for shipment. You can speak with your local UPS or FedEx folks about how they'll handle such shipments. You'll want to price your auctions accordingly, if needing to ship properly via HazMat packaging.
Works pretty well. I've used GB many times for both purchases and sales. Great visibility. And if you're willing to ship, it opens up the entire country to potential buyers of your stuff.
