This is a question that needs to be answered by a laboratory with pressure testing equipment. I don't recall such a test being done. Perhaps another correspondent does, and can enlighten us.
In the absence of that, we have to fall back on experience. The technique of cleaning lead from a barrel with jacketed bullets has been recommended by people with a lot of experience for about a hundred years now, and I have never heard of any problems associated with it. I have been doing it for over thirty years, with nary a hint of high pressure.
Incidentally, it is well established by pressure testing that lead bullets generally develop less pressure than jacketed bullets with the same load, all else being equal. A typical example is Winchester data for the .44 Magnum with 296 powder and 240 grain bullets. With the lead bullet, 25 grains of powder develops 1560 fps at 37,500 cup, while with the jacketed bullet, 24 grains of powder develops 1430 fps at 38,000 cup.
Hopefully, someone can refer us to a scientifically conducted test that will settle the matter without conjecture.
In the absence of that, we have to fall back on experience. The technique of cleaning lead from a barrel with jacketed bullets has been recommended by people with a lot of experience for about a hundred years now, and I have never heard of any problems associated with it. I have been doing it for over thirty years, with nary a hint of high pressure.
Incidentally, it is well established by pressure testing that lead bullets generally develop less pressure than jacketed bullets with the same load, all else being equal. A typical example is Winchester data for the .44 Magnum with 296 powder and 240 grain bullets. With the lead bullet, 25 grains of powder develops 1560 fps at 37,500 cup, while with the jacketed bullet, 24 grains of powder develops 1430 fps at 38,000 cup.
Hopefully, someone can refer us to a scientifically conducted test that will settle the matter without conjecture.