How to Prevent Barrel Leading from Cast Bullets

Barrel leading is the most common complaint from cast bullet shooters. Lead deposits build up in the rifling, accuracy degrades, and cleaning becomes a chore. The good news: leading is almost always preventable. It's a symptom, not an inevitability. This guide covers every major cause and fix.

The Four Causes of Leading

Nearly every leading problem traces back to one of four root causes:

1. Alloy too soft for the velocity
2. Bullet undersized for the bore
3. Insufficient or wrong lubrication
4. Velocity too high for the alloy and bullet combination

Diagnose which applies to your situation before reaching for a solution. Most cases involve more than one factor.

Diagnosing Your Leading Pattern

Leading Location	Most Likely Cause
At the forcing cone (revolver)	Undersized bullets jumping the gap
First few inches of barrel	Alloy too soft, gas cutting the base
Throughout the bore	Undersized bullet not engaging rifling
At the muzzle	Bullet tumbling, poor fit, or no gas check on rifle
Consistent streaks	Lubrication failure or uneven lube application

Fix 1: Harden Your Alloy

This is the most common fix. If you're running wheel weight alloy at 1,300+ fps and seeing leading, you've exceeded what that alloy can handle. Move to Lyman #2 (15 BHN) or heat-treat your wheel weights to push them to 18–22 BHN. Match alloy hardness to velocity using this rough guide:

• Under 1,000 fps — wheel weight or softer is fine
• 1,000–1,200 fps — wheel weight minimum
• 1,200–1,500 fps — Lyman #2 or equivalent
• 1,500–2,000 fps — heat-treated wheel weights or linotype + gas check
• Over 2,000 fps — linotype minimum + gas check

Fix 2: Size Your Bullets Correctly

An undersized bullet is one of the most overlooked causes of leading. If the bullet doesn't fill the bore, gas blows past it, melting and stripping lead from the bearing surface. The standard recommendation is to size .001" over groove diameter. Slug your barrel — push a soft lead ball through with a rod and measure it — and size accordingly.

Fix 3: Improve Your Lubrication

Cast bullet lubricant does two jobs: reduces friction between bullet and bore, and provides a gas seal that supplements the bullet's fit. If your lube is inadequate, leading follows. Key points:

• Use a lube appropriate for your velocity — soft lubes work for low velocities, harder lubes for higher velocities
• Make sure lube grooves are completely filled — not partially applied
• Store lubed bullets in a cool location; soft lubes can migrate out of grooves in heat
• Pan lube versus pressure lube matters — pressure lubricating with a lubricator-sizer produces more consistent lube application

Fix 4: Reduce Velocity

Sometimes the right fix is simply to reduce your load. A 10% reduction in velocity can dramatically reduce leading and often has minimal impact on practical accuracy at handgun ranges. Many cast bullet shooters deliberately run mid-range loads for exactly this reason — less leading, less recoil, and nearly identical accuracy at 25–50 yards.

Removing Existing Leading

Once you have leading, get rid of it before it gets worse. Methods in order of preference:

1. Lead-Away cloth — The fastest method. Wrap around a patch or bore brush and run through the barrel.
2. Lewis Lead Remover — A specialized tool that presses brass screen against the bore to scrub lead out.
3. Chore Boy copper scrubbing pad wrapped on a jag — Budget version of the above. Effective on moderate leading.
4. Mercury-free lead solvent — Chemicals like Shooter's Choice Lead Remover dissolve lead deposits. Useful for severe cases.