Thank you for adding info to this post.
.36 caliber black powder bullet molds typically produce projectiles ranging from (0.360) to (0.375) inches in diameter.
I was thinking I'd read .375" to .380", thus the range I put into my posting.
The exact diameter required depends on whether you are casting round balls or conical bullets,
I'd not really read about or thought about differing cast diameters for round balls vs conicals. Considering what you mention below, however, makes complete sense.
and the specific manufacturer of your cap-and-ball revolver or rifle.
My understanding is that original cap-and-ball revolvers made during their "golden age" varied wildly in the dimensions of both the cylinder chambers and barrel groove diameter, and to reiterate, I was thinking that I'd read somewhere that the cylinder chambers were as large as .379" in the most egregious extremes.
I really don't have any information (or even misinformation) on the state of dimensions for modern reproductions.
Common Mold Diameters & Uses
- (.375) inch: The most common standard for .36 caliber round balls. This size is ideal for most modern Italian reproductions of Colt 1851 Navy, 1861 Navy, and Remington pocket revolvers. When rammed into the cylinder, it shears a thin lead ring, ensuring a tight seal. Available from makers like Lyman #2665375 Round Ball Mold and Lee 2 Cavity Round Ball Mold.
- (.360) to (.365) inch: Typically used for conical bullets in cap-and-ball revolvers. Conicals are sized to fit snugly into the cylinder's mouth without needing to shear lead the way round balls do.
- (.375) inch (Conical): Available as part of the Lee Conical Bullet Mold lineup, these 130-grain conical bullets are designed for reproduction cap-and-ball revolvers.
I am the "proud owner" of round ball molds having three different nominal diameters: .360", .375" and .380". However, I've yet to purchase my first cap and ball revolver. I'm eyeballing the Uberti repros, both their 1851 repro and their 1861 repro. At some point, my future state will be to own an example of both models (hopefully I'll be able to stop myself from going too crazy after that).
Why Diameter Matters
- Revolver Cylinders vs. Bore: The chambers on a .36 caliber revolver cylinder are generally wider than the actual barrel bore (which typically measures around (0.357) to (0.360) inches). The oversized bullet is necessary so that the loading lever shaves off a ring of lead as it seats the ball, creating a perfect seal and preventing chain-fires.
I thought that creating a complete seal and preventing chain-fires is the job of either an underwad or of a mouth-of-chamber sealant. But what you're saying is that the fit of ball-to-cylinder is the primary seal. Correct?
- Round Balls vs. Conicals: Because they have less surface area in contact with the rifling, round balls need to fit tighter than conical bullets. Standard round ball molds usually cast at (.375), while conical bullet molds often drop closer to (.365).
I'd not considered bearing surface. Makes sense. The more lead that is shaved from the ball upon seating, the greater the bearing surface increase. Do not most conicals for blackpowder revolvers also incorporate a hollow base in their design for the purpose of increasing the bullet seal?
