Updated - Original Spencer Cartridge Ballistics - Updated

[ndnchf]

El Supremo - no leading, the rapine bullet carries a good size lube payload. No significant blowby either. There's always a little residue in any BPCR action, this is no different. To clean I just drop the block, wipe it and the receiver recess off with an oily rag and its good to go.  Very little residue on the rag. The iron sights are a challenge for my eyes too. I bought a Merit optical attachment for my glasses. It helps a lot. Is your Spencer a carbine or rifle? I look forward to hearing your results.

[El Supremo]

Thanks Ndnchf:
I have a rifle and two carbines.  They are mint, unfired but have a bit faster twist at approximately 36".  Have had them for some time well before the imports surfaced.  Am just about finished having custom bored, nose pour molds casting a .515" OD, 320gr bullet in 16Bhn metal.  The prototype mold is made from Mehanite cast iron.  I have various black ONLY powders for testing in Rocky Mountain turned brass cases taking large rifle primers.  The bores are .510" and I plan to size to .512", but have sizing dies for .511" and .513", also.  CH4D dies and their proper shell holder fit great.  These cases are dimensioned to fit the chambers with very little expansion.  Still, I plan to anneal in molten lead each reloading and full length resize.  Only a crimp that rounds the case mouth should be enough.  No wad at first.  Plan on 35 FFg and will try 40 for 100 yds if it fits.  The Merit iris is a widely accepted sighting aid.  Started in a YMCA basement range at age 10 and have used one for the past 60+ years.  Spare suction cups are available.  That hammer fall is the challenge.  Dry firing with a well cushioned snap cap or primed case and four power scope at 50 yards will tell me how to hold it on the bags.  I estimate the barrel time  at 1050 fps will have the rifle recoiling approximately .200" before the bullet leaves the barrel.  That's about twice as long as with most of my other heavier and slightly faster BP bullet rifles.  Again, may I compliment you on your grouping and consistent velocities.  You have clearly mastered the rifle with good load development and great bench technique.
Regards,
Kevin