I'm not liking all the mess (wasted powder) that I'm getting with the LEE unit.
I'd suggest you contact Lee on the problem - my bet is that you have something wrong with your used stuff. Although many people say these powder measures are prone to leakage, in my opinion, it just ain't so. Some might have a problem, but mine sure do not. But there are several articles in the Lee Support center that deal with the problem, so it obviously does exist for some.
I have two Lee auto-disk measures used on a Pro 1000 press, and one Lee Pro auto-disk measure used on my turret press. I load a LOT of ball powders (296, H110, HS7, HS6, Accurate No. 5 & 7, 2400, WW473, and WW452), and my leakage from any of them is absolutely minimal. I never see any flakes or grains on top of the turrets unless I slop a little when changing the discs.
I have always been real impressed that the two standard auto measures are as tight as they are, since there is nothing special in them to seal the joint between the disk and the hopper (one is relatively new, and one is from the 80s). The Pro auto disk does have a soft rubber wiper in the base that is specifically intended to seal any gap and prevent cutting of larger flakes. You might have a problem with that.
But since your unit is used, it may have another easily fixed problem - some measures were shipped a few years back that did not have the base fully inserted into the body. In these units, the disk actually is pushed too far out and overshoots the drop hole. When using large diameter disks, the edge of the disk hole will actually go clear past the base of the measure and dump some powder out below it! The easiest way to tell if this is your problem is to just empty the hopper and look down at the base where it opens over the hole in the disk. Is the hole centered under the hopper? If so, all is fine, but if the hole seems a but off-center, then you need to fix it. See this support article:
http://leeprecision.net/support/ind...forward-beyond-the-face-of-the-powder-measure
The fix is quite simple and does not take any significant effort at all to seat the drop tube properly.