I picked up a former LE 4566 a few years ago and with the scarcity of new parts and affordability of parts kits, I picked up a few parts kits recently and assembled the perfect pistol kit. Pictured below is the 4566 frame with a 4516 upper on it, the original 4566 upper and a 4506 upper. All work perfectly and I have an abundance of spare parts now. I also purchased a 1006 parts kit to use with my 1076 and surprisingly the 1006 upper works great with the 4566 lower as well. The 45 mags hold 9 rounds of 10mm and feed just fine. I'm currently working on a 4013 upper to convert to 10mm and use on the 1076 frame and I will have all three barrel lengths in 10mm as well.