Leading with 5744

[Roosterman]

I seem to have leading problems with 5744 no mater what bullet I'm shooting. Lead is in the 1st inch of the breech. What's up with that?

[PJ Hardtack]

What calibre? What bullet diameter? What bullet lube?

I've shot 5744 for years in both 45-70 and 50-70 loads, using 28 grains for both. I get a little leading near the muzzle of my 30" Military Rifle barrel, but none with the carbine.
I'm sizing Lyman 515141s to .512 for the .510 bores and using SPG lube with both smokeless and BP.