Greetings All,
I too am a user of Puff-Lon in the 45-75WCF in combination with the 5744 powder. The level of unburned powder in my Uberti 1876 using this load is very little, and for this reason I continue to use the product. Now I worked up the load from scratch with Puff-Lon in ALL levels of development so it has always been part of the load testing. I have read recently of some folks having problems using filer with 5744, or so it was reported. The details weren't complete but it got me to thinking. I went to the makers page for 5744 and did a little reading. They mention Puff-Lon by name in some of their tests. Not content with that , I emailed the good folks in their technical dept and asked if they saw any problems using Puff-Lon with 5744. I was expecting a good scolding for using a filler or at the very least be told I had committed sin of a terrible level, but nope not what I got back. I hesitate to share the exact wording as I wasn't given permission to share private correspondence but lets just say they didn't seem to have any problems with what load I am using or how I created it. My humble $.02 worth is that in reloading you take responsibility for your own work and with any discussion of reloading using what is shared is at your own risk, bottom line is just be careful and follow the directions it comes with. For myself I am pleased with the combination of the 5744 and Puff-Lon. Buffalo Arms is one source of the product and you can order it direct from the Puff-Lon site. Best of luck with the rifle and finding a load it likes.
PB