I'd be interested in others thoughts on this as well.   

I've tried a thin card wad under the bullet when using a Russ Weber breech seater.  Twice the wad came back out with the seater and fell into the action.  That was a major pita.  The first time I didn't notice the wad fall into the action and it took me a while to figure out why I couldn't close the action

Now I'm only using under bullet wads with black powder.

Chris.

Fellow I shoot BPCR/BPTR with shoots quite a bit of CBA benchrest with smokeless in his 38-55 rifles. He uses floral foam wads to keep the powder at the bottom of the case and breech-seats his bullets. He tells me that both his Hepburn & High Wall in 38-55 will hold 1MOA out to 200yd, though I've never ask about his load info. The reason I mention is that floral foam will not work very well with the 38-56, being a BN case, but am wondering if something like puf-lon or other "cotton like" material would?

Finally got to the range last Wednesday to try the 4227 against my usual load of 62 gr of PP Wano, the results were as follows.
WANO 62 gr
Average MV 1260.7 fps, ES 16 fps
18.5 gr 4227  1221 fps, ES 13 fps
Armed with this information I decided to increase the 4227 load to 20 gr, the result was an increase of MV to 1722 and an ES of 7 fps, extraction was difficult, the primer fell o9ut on extraction and later when I tried to reload the case it would not go into the shell holder. Clearly a bit too much powder methinks.
I have re loaded with 18.8 gr of the 4227 and I will try that later.
As a matter of interest my 62 gr load of PP shot into 1.205 at 100 meters and the two shots I fired with the 20 gr of 4227 were .540" apart, I considered it unwise to continue with the 20 grain idea.
The 18.5 gr 4227 group I fired went into a group of 1.215" on a day that was far from perfect.
I trust this information may be of some assistance to anyone with a 38/56 who may be considering straying to the dark side.
Mike.