Prof,
The spherical propellants don't pack down as much as stick powders do, but their fine grains clog up the Perfect and also my favorite stick powder measure, the JDS Quick Measure. Some folks disassemble and deburr the casting of the Perfect and tighten it a little and claim to improve the leakage problem, but the ones I have in my range box both do best with stick powder and stubby larger grains, and I haven't bothered to alter them for those applications.
The Hornady and Uniflow and Redding drum measures all do well with the spherical powders. So do horizontal metering cavity measures like the Lyman 55 or the expensive Harrell measures. So, I expect, will the new
Lee Classic cast measure, which is a metal version of the Perfect and should not have the fit and leak problems the molded plastic parts in the Perfect do. It also has the advantage that they will sell you separate metering drums so you can leave them set up for a particular load and swap them out easily. Call and ask Lee about it with fine powders and describe your problem with the Perfect and make sure it gets around that, but I'm pretty sure it will. It is new this year, and don't have one to play with yet. So I am just surmising from the description that this will address your problem and operate and adjust the same way the Perfect does, which will make it easy for you.
One thing to watch for if you switch measures is a minimum charge capacity number. The Harrells have a 6 grain minimum and my Redding BR-30 has a 10 grain minimum. These are intended for rifle cartridges. They are not appropriate for some handgun loads, obviously.