OK, who would have thought peep sights would be so much fun? I picked up a used d54 (.22) that came with a Williams rear peep sight and a variety of front sight inserts. It has both been a challenge and a blast learning how to shoot with them 
And yesterday's shooting after switching to an aperture front sight (25-yards, rested 5-shot groups):
And yesterday's shooting after switching to an aperture front sight (25-yards, rested 5-shot groups):