This is largely a strategy of grinding off the reinforcement product that was extra to reinforce the buffer tube/extension area, and reprofiling the realm to really make it resemble the first A1 region. This might include some welding or filling of some sort. Use the photographs under for example: The https://gold-cup-trophy-colt-4523333.hyperionwiki.com/961570/colt_combat_elite_commander_45_acp_for_dummies