Ok, custom might be a bit generous.  How about "bubba'd without a dremmel"? 
1884 Springfield action and lock
Barrel: GM Sharps Rifle #1 Heavy Rifle Barrel .458 1:18" twist
Stock: Hand whittled walnut, Goncalo Alves (jobillo) butt extension (yup, I cut it too short), Asian buffalo horn butt plate, pewter nose cap.
Sights and trigger from T/C Renegade
Trigger guard Track of the Wolf Hawken style.   
Metal finish: Duracoat.   

Sorry, been out of the net for a few days, son contracted Lyme Disease in Kroatia. Been working to get the family back here for better treatment...

SS

You might want to consider using a Lyman mold known as the "gould express" about 330-340 gr. it has big enough lube grooves for black powder. for shooting big game animals it has worked very well for me. I ground the hollow point pin off to make a flatnose instead of hp. In my gun, (45/75 '76win) the 1rst shot is in the same group (2-1/2") as the last shot and I don't have to blow to soften fouling. plenty of penetration. just my .02
good luck with your project, 
kootne

BigOtto, I just reread one of your posts refering to using a 7/16" (.4375 nominal) to punch your wads (not big enough to fit the grooves) and that may lead to combustion forces being impinged on the corner of the base which would be unprotected but is the part that needs the most protection as the bullet exits the muzzle. besides it probably wouldn't center evenly or consistantly which don't help. google up Buffalo arms, I'm sure they have correct dia. wads, or call John Walters 405-799-0376. John King in Kila, Mt. also sells them but I have lost his phone #. or I'm sure Buffalo arms has punches to make your own.