I think I have a answer to the question of two different lenghts of chamber brushes on the M3A1 conbination tool. The Italians did have a variant of M3A1 combination tool for their BM59 rifles. This tool can be identified by the hex projection that acts as the pivoting piont for the blades. The brushes for these tools would be by design for the 7.62 mm NATO chamber and not the .30-06 chamber. Why the shorter brushes show up on M3A1 tools not made/modified for the BM59 is still unknown. Check your brush lenght. If you have a M1icon in 7.62 mm NATO a short brush is what you want.