Looks good!!Paint job and all,All the paint does is protect it from rust,if you dont mind how it looks -who cares? If you ever get the hankerin you can allways refinish it anyway,thats how I look at it
As far as the retainer-see if the locking pin is buggered up somehow and not locking into the groove all the way.Or the groove on the barrel is a tad to big,if the groove is a bit oversized you might be able to throw a bead of weld on the locking pin and file to fit
Or you can take a punch and put tiny dimples on the edges on top of the slot of the barrel.