Another old article from the old Sixgunner.com website

[JimT]

This is an old newsletter from a cast bullet supplier we used more than 20 years ago. They are no longer in business.

Leading Defined
from the Mid-Kansas Cast Bullet Newsletter

Used by Permission of Mid-Kansas Cast Bullet., Inc.

Deposits of bullet alloy that have been smeared into the surface of the gun's bore. In extreme cases, it will build to the point where the rifling is completely choked with deposits and the barrel appears to be smooth-bored. Once leading begins, it will have a tendency to strip alloy from the next bullet which builds the deposit with the next shot. Each successive bullet fired will "iron" the lead into the surface of the bore and make it more difficult to remove the deposit.

Chamber and Forcing Cone Leading

This is normally caused by shooting a bullet that is too hard (BHN too high) for the velocities used. Either use a softer alloy, or increase the charge (within published loading data, of course!) to correct this problem. This can also be caused by shooting a bullet that is too small in diameter. Revolvers will lead in the chamber and forcing cone while closed breech weapons will lead in the chamber and the beginning of the rifling area. Have the cylinders measured for revolvers and size the bullets to them, not the bore (unless the bore is larger than the chambers, in which case the problem will have to be corrected by a gunsmith or the factory) and measure the bore in closed breech weapons to determine proper bullet diameter. Rule of thumb says the bullet should be .001" larger than the bore or equal to (or very slightly larger than) cylinder diameter in a revolver. If the alloy is soft enough, you can get away with a slight "push fit" in a revolver cylinder, but certainly the bullet should be large enough to not fall through the small diameter portion of the cylinder freely!

Breech Leading

This is lead fouling that begins in the rifled portion of the bore, but after the chamber or forcing cone, and extends into the bore for a distance of up to several inches. This is normally caused by shooting a bullet that has a low BHN (too soft) for the pressures or velocities used. The bullet will actually strip as it enters the rifling as it does not have the strength to properly engage and begin rotation due to the forces pushing it through the barrel. It doesn't mean it's a bad bullet alloy, it just means you are driving it too hard. If you want to go faster, you will need a stronger alloy with a higher BHN number. Alloys must be used which fit the application. There is no such thing as a "magic" alloy that works for every single application!

Bore Leading, Muzzle End

When lead fouling occurs at the muzzle end, you have run out of bullet lubricant. Either use a better lube, or more of it to correct the problem. If you can, use a bullet with more, or deeper and/or wider lube grooves. After firing a box of cast bullets, say 20 to 50 rounds, there could be a lube "star" on the muzzle. This indicates that there is simply left over lubricant and the bullet exited the muzzle with plenty of lube. If, however, you find a lead "star" instead you need to try something different as the bullet ran out of lube. You may be able to simply reduce the charge (lower velocity) and correct this. The alternatives are use a better lube or a different bullet design that can carry more lube. As an example, there are .45-70 Govt. 405 grain bullets on the market with only a single lube groove. Barrels over 16"-18" long using this single lube groove design bullet will exhibit muzzle leading after only a few shots! Frankly, the only reason this bullet exists is that it is simpler to manufacture! The three groove design used by Mid-Kansas is much more difficult to cast (they stick in the moulds!) but is a much better bullet for the shooter! As we have your interests in mind, we have devised methods of casting this bullet style on a volume basis to bring you, the shooter, the best product available.

Bore Leading, Entire Bore

Normally, this is caused by shooting a bullet that is too small in diameter for the bore. If the bullet doesn't seal the bore, gas will be able to escape past the bullet causing a cutting action similar to the way a cutting torch cuts steel. By the way, gas cutting will only occur if gas can flow. The propellant will not cut the base of a lead bullet if the bullet properly fits the bore! There is simply too much physical mass to heat to the melting point of lead (about 600-700F) in the short time a bullet is exposed to the propellant gas to bring it to it's melting point! If you want proof, examine wads used in shotguns or black powder cartridge loads after firing. They may show slight darkening, but won't be consumed in flames either! If the powder won't melt the plastic or burn up the cardboard, why would it melt a bullet base? The answer is, it can't. Damaged bullet bases are caused from other things, principally incorrect bullet fit to the bore or a bad bullet to begin with!

Optimum Accuracy

Cast bullet accuracy is directly related to the pressure levels your cartridge is loaded to. If the operating pressure is too low relative to the bullet's BHN (hardness), you will not achieve obturation and the bore will not seal. This will cause gas leakage and erosion (gas cutting) that causes leading at low pressure and low velocity! Optimum accuracy occurs at a point just below the pressure levels that induce breech leading for a given bullet alloy. In other words, if you are shooting an excessively hard bullet for Cowboy Action pressure levels, you will get leading, usually in the forcing cone or chamber area. There are several different alloys that we use at Mid-Kansas Cast Bullet. All are sourced from foundries and are specification alloys. The first is our standard bullet alloy, #26. This consists of 2% tin, 6% antimony and 92% lead. This alloy yields a true, measured BHN of 16. This is a very hard, tough alloy that will function up to velocities of 12-1,400 fps in most firearms. We have customers that report using our .45 ACP 155 grain SWC's at 1,500 fps with no leading. Our own testing has shown our .45-70 Govt. 405 grain bullets are capable of 1,700 fps in a Browning High Wall without leading. The second alloy is our Cowboy Action Alloy™ which consists of 2% tin, 4% antimony and 94% lead. This alloy yields a BHN of 10. This alloy is recommended for low pressure and low velocity loadings commonly encountered in CAS sports. It has also found considerable use in black powder cartridge loadings when lubed with SPG. The third alloy used is referred to as 20:1. This is a blend of 95% pure lead and 5% pure tin. It is quite soft and is used extensively in black powder cartridge rifle shooting. This alloy will measure BHN 9. Mid-Kansas also carries in stock pure lead. This is referred to as foundry chemical lead and is as pure a form of lead as can be obtained for a reasonable price. We are currently not casting with this metal, but offer it for those who wish to cast muzzleloader balls. It has a BHN of 6 and is available in 25 pound "pigs" which may be cut into 5 pound ingots easily by severing a small connecting strap between the 5 pound ingots. We will offer it in lots as small as 5 pounds. Being pure, it is relatively expensive. As an alternative for the muzzleloader on a budget, we also offer scrap plumber's lead. This is reclaimed flashing lead that cleaned and formed into small ingots (roughly one pound) but is not as pure as the chemical lead. It is, however, roughly half the price!