I brought a healthy supply of Federal's 158 grain .357 magnum load from Wally World and I loaded 5 speed loaders, the gun, and the block. That means 84 rounds before I touch a cartridge with my hands.
After that I reloaded the block, speed loaders, and revolver and did it again. Before I new it I went through 168 rounds
. That was the fasted I have ever gone through ammo! Comparing them to HKS loaders I would say they are easier to turn but not so much that you would accidentally release the rounds. Also, they fit the Security Six better than the HKS loaders. The HKS one always fit my K frame S&W revolver perfectly but it was slightly off on the Security Six. Now, I need to try it with my m65 to see if it fits both equally well. Finally, because they are relieved and not circular they fit better with my over-sized grips.
Here's a target of one set of 84 rounds at 14 yards: