This is a topnotch hornady accessory - Hornady Lock-N-Load AP Primer Pocket Swage Tool For .223/5.56mm Only

If you work with Lake City or other military brass, you need to swage the primer pockets. If you process lots of brass, then I would recommend this swage tool. It takes a bit of trial and error to get the swage tool properly set, but once you get it set up, it's golden. Look on youtube to see how to attach a tube to the exit die. This setup is so fast that you need to tube to handle the swaged cases exiting the press. Processes a case about every two seconds.