6.5fan,
Not a fan of any type of crimping in ARs, and I don't use them myself in my own loading. However, I've had to work with a variety of these professionally over the years, so have had some experience with them. Of the lot, the Lee Factory Crimp is far and away the best out there. One of the various taper crimps (Redding, RCBS, whoever) would be second place.
One of the keys to AR accuracy is using sufficient neck tension, and avoiding the crimp altogether. I like bushing dies for this very reason; it lets you set the degree of tension to a much greater degree than any other method that I'm aware of. I normally use an expander ball (preferably carbide) but select the bushing that leaves it with the faintest kiss as the ball passes back through the neck. If you run an expander ball that's .002" below bullet diameter (.222" max), that should give you a decent grip while not overworking the necks. Important to remember that when you trip the bolt, what you're dealing with here is the world's heaviest and most expensive kinetic bullet puller. The fact that your bullets are only pulling .002"-.003" tells me that you're pretty close to the max already. I've done testing using even M193 military ball ammo, complete with asphalt neck sealant AND crimp, and still seen this level of movement. It's just a fact of life with the ARs, but so long as you're not moving too much more than this, it's nothing to loose sleep over. You're doing fine here.
