Mastercast Bullets of Enon Valley PA makes a very nice 215 grain cast LSWC bullet for the .429 caliber guns, especially the .44 Special. Unfortunately, none of my loading manuals list any 215 grain loads.

I use Unique for my .44 Special loads and have found 6.5 grains behind a Missouri cast LRN 240 grain to work well in most of my guns.

For the 215 grain bullets , I was thinking of using either 210 or 225 grain data and going form there.

Anybody have pet load using 215 grain bullets and Unique? - Or even Bullseye?

Lyman CAST bullet manual lists data for a 210 lead bullet. 44 Special. Several other powders but I do not know what you have.

Unique 6.3 to 7.7grs. The high load is listed as their best load but of course all different test parameters.

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Still Running Against the Wind

Have a Lee 200 LRNFP mold that drops 217 grns (go figure!).

Works well w/ 7.2-7.5 grns Unique.

It has been a while since I loaded the 44Spl but, when I did, I used a 200gr LRNFP from Lee's mould and 4.5gr of Bullseye for a competition load for PPC.

Light recoil and accurate.

With a 44Spl, you can go from mild to wild. Elmer's loads can be tweaked a bit and you can launch one of his 250gr bullets at well over 1000fps.

It really all depends on what you want from the firearm.

If you haven't done so already, I recommend slugging your chamber throats, forcing cone, and barrel (I've never been able to measure the 5-groove rifling, though).
I've found commercial cast bullets mostly too hard and .429 too small to obdurate and seal the the chamber throat, giving less than stellar accuracy and leading to boot. The bullet should be as close as possible to throat diameter, which I always found to be .431 in all my .44s, smith and Ruger. I cast my own for years but no longer have time, though I still have a supply.
I think I read Penn bullets can provide different diameters/hardness.