Actually, if one examines what is typically found in polishing/lapping compounds, you will discover pretty quickly that the grease/carrier is almost always water soluble, meaning it is water based, and has no load or shear strength, and the abrasives are pretty intense, typically, silicon carbide, garnet, boron carbide, aluminum oxide or diamond. The grit that accumulates after firing a gun, lubricated with a good quality, EP grease can't begin to compare with these, and good quality EP grease will hold a quantity of debris in suspension, where it can't hurt anything, by design.
I think it was McIntosh who originally compared the two, and it is a bit misleading. The debris that results from firing a gun, if mixed with a good quality EP grease, will be a very inefficient lapping compound.
That doesn't mean you shouldn't keep it clean, but, you have more time and far better lubrication than if you did use valve lapping compound.
Best,
Ted
