I tried to reload for my son's 5.7X28. You need to know if you are loading for a pistol or a rifle. A non-comercial load that shoots well out of a pistol will blow up the rifle. I used True Blue to reload for the pistol only. To get the pistol to function well I was getting brass back that pretty much had the shoulders completely blown out. The brass is very hard to process and like stated before, you can't tumble the brass due to whatever the coating is on the brass. To bypass that particular problem we would use simple green and warm water in a left over 8lb powder bottle to get all the grime off the brass. If you get off on shiny clean brass, this round is not for you. Due to the type of slug we were using, it was very important to crimp the reloads. Needless to say, if the shoulders are comletely blown off the case, trimming the brass was needed after every load. Trying to trim the little tiny cases was just no fun at all. Mind you, I like to reload and take pride in my work.
I tried everything I could think of, much less all of the forum reading I could do and never found a successful, well functioning reloading recipe. I have been reloading since 1979 and I have loaded for every firearm my family and I own. I'm not a beginner but I just couldn't figure the 5.7X28 out. I am certain the biggest problem I was facing was not having access to the powders used by the commercial manufacturers and just couldn't find the right powder/bullet combo. It finally came down to my son selling his FN because it was just too expensive to shoot. We like to shoot a lot of rounds and the 5.7 was just too expensive to feed.
This whole nightmare happened about 8 or 10 years ago so I really don't know what is available for reloading the round but if I had to do it all over again, I would just say no.
Sorry for the bad news but it is the honest truth.