This is what your array of parts should look like.
Make sure you do NOT loose the spring circled in red in the picture. If you do then your weapon will have to be a manual reloading gun.
crwdns2944171:0crwdnd2944171:0crwdnd2944171:0crwdnd2944171:0crwdne2944171:0
crwdns2931507:0crwdne2931507:0
crwdns2931509:0crwdne2931509:0
crwdns2931511:0crwdne2931511:0
crwdns2931513:0crwdne2931513:0
crwdns2931515:0crwdne2931515:0
crwdns2931517:0crwdne2931517:0
crwdns2931519:0crwdne2931519:0
crwdns2931521:0crwdne2931521:0
crwdns2931523:0crwdne2931523:0
crwdns2931525:0crwdne2931525:0