I recently purchased a Government Model in electro. nickel serial number beginning with 70B. I got a great deal on this pistol and it's very accurate. The only problem I am having with it is the slide does not lock back after the last round is fired. I only have 2 magazines, the original Colt mag. that came with the gun, and I used my friends Colt mag. that came with his Government Model also an old 70 Series. Today I also had one "double feed" out of 50 rounds of Remington 230gr FMJ. Could any of you guys tell me what might cause this problem? Also could the double feed be related to this? Thanks.