Ian
Notorious member
I don't think the whole bullet will flow, but it might draw out in the middle.
Tin forms an intermetallic bond with antimony in approximately equal molar amounts, creatng a strong, tough, but malleable lead alloy due to its fine grain structure and small shear planes.
A low-antimony alloy will extrude and draw quite easily because of the large shear planes (think of it as a deck of cards). Too much antimony by itself in lead makes a hard and brittle alloy, but when tin is added the result is more malleable, like stiff putty. However, the tin/antimony intermetallic puts up a fight when you try to cram it through a smaller hole, creating much resistance and internal frictional heat as energy is applied to change its form. Heat weakens the alloy. Low-antimony alloy will extrude with much less resistance, less force needed on the bullet base, and while building less internal heat. The catch when using a tin-starved alloy is the surface of the bullet is relatively weak and cannot take as much abuse without deforming when banging around in the throat at odd angles.
My thought is that powder-coat adds just a hint of tough, slippery skin that helps the bullet guide to center and engrave (a little = a lot here), thus allowing a much softer alloy than normal to be used without the bullet totally losing its form when kicked in the pants. Tin may or may not help the bullet maintain its form, it depends on a lot of things like how much the bullet is being squeezed, how much jump, how steep is the pressure curve of the powder, how much engraving resistance and inertia the powder is working against, and so on. The slick paint changes the dynamic one direction, the tin changes it another. Only shooting will tell us for sure whether these things are for the better, or not, and you can bet wvery situation will be different so it isn't likely a firm guideline can be easily established here.
Tin forms an intermetallic bond with antimony in approximately equal molar amounts, creatng a strong, tough, but malleable lead alloy due to its fine grain structure and small shear planes.
A low-antimony alloy will extrude and draw quite easily because of the large shear planes (think of it as a deck of cards). Too much antimony by itself in lead makes a hard and brittle alloy, but when tin is added the result is more malleable, like stiff putty. However, the tin/antimony intermetallic puts up a fight when you try to cram it through a smaller hole, creating much resistance and internal frictional heat as energy is applied to change its form. Heat weakens the alloy. Low-antimony alloy will extrude with much less resistance, less force needed on the bullet base, and while building less internal heat. The catch when using a tin-starved alloy is the surface of the bullet is relatively weak and cannot take as much abuse without deforming when banging around in the throat at odd angles.
My thought is that powder-coat adds just a hint of tough, slippery skin that helps the bullet guide to center and engrave (a little = a lot here), thus allowing a much softer alloy than normal to be used without the bullet totally losing its form when kicked in the pants. Tin may or may not help the bullet maintain its form, it depends on a lot of things like how much the bullet is being squeezed, how much jump, how steep is the pressure curve of the powder, how much engraving resistance and inertia the powder is working against, and so on. The slick paint changes the dynamic one direction, the tin changes it another. Only shooting will tell us for sure whether these things are for the better, or not, and you can bet wvery situation will be different so it isn't likely a firm guideline can be easily established here.