Deacon,
You can shoot BP lubed bullets with our lower velocity pistol loads with "smokiless powder" and they do fine. Especially if you have a Big Lube bullet or a larger groove variety. Unfortunately, I'm not sure who sells BP lubed bullets anymore. I know people use the Desperado Cowboy Bullets
https://cowboybullets.com/45-cal-200-grain_p_24.htmlI know one pardner buys then "unlubed" and then pan lubes them. Others have told me they work fine with BP with the lube they come with. I have no experience with them.
On your Dillon you can get a quick change adapter for your powder measure and just switch it. I wouldn't run real powder through a Dillon Measure but I have a Brass Hornady Black Powder Lock-N-Load measure on my Dillon 650 with a quick change to allow me to go between my .44 caliber and .38 caliber heads. I posted a picture below. I load all of my BP pistol and rifle loads on a Dillon XL-650 Progressive and my BP shoptshells on a MEC 600 Jr MkV (but I hand drop the powder that is why I use the 600 instead of a progressive shotshell press)
I just looked for a picture of the Black Powder measure and I think they may have discontinued them! This is ridiculous I leave home for two years and the world falls apart!
It doesn't show up very well and that is a smokeless powder Lock-N-Load on the left but I posted it to show the mechanism that makes it "automatic" and to show that die on the bottom. I have two of those dies and two mouth expanders I just loosen a screw for the arm, unhook the spring and move the measure.
Well look at the Lee Through Powder Die for your set up. You could hand hold a measure above it ( I have done that with an RCBS "Little Dandy" measure, I looked and whew!!! they still make those and not priced bad, but you have to buy individual rotors, I have a box full) Just dip your Real BP. I'm not sure what to tell you about a substitute in a mechanical measure. Someone else chime in here. What does APP say about that?
You should be able to use the exact same set up on all of your dies on you RL550 (except your charging station), your just changing powders . Yo can remove your measure (simple to do and leave the screw in portion in) and stick a funnel on thee and drop your charge of APP. I can't remember it's been 20 years since I had a 550, does the charging station also bell the case mouth? Hmmm, I'll bet someone makes an accessory to allow you to use that expanding die and still drop through a charge. I'll look (you have enough to worry about). Actually don't worry it is easier than it sounds.
~Mako