This is the worst gun I currently own:
A 1948 Colt Detective Special.
It has a cut-away trigger guard and the hammer spur bobbed. These are NOT factory alterations. They're not done poorly, but the finish wasn't cleaned up following the alterations. It still carries the original plastic - "Coltwood" I think it was called - grips. The left grip is cracked at the heel. (I would attach a picture, but my camera has gone flat. Perhaps later.)
It is a representative piece of a law enforcement officer's revolver of the 1950s and 1960s. Based on information of where it was sold originally and where I bought it, it was used in Los Angeles County, California.
The problem it has - which makes it the worst gun I own - is the standard Colt lockwork inside the revolver. When I purchased it - as a collector item, not a shooter - the timing was so bad I felt it unsafe to shoot. I spent some money to have it 'timed' and the gunsmith who did the work said it was '... as good as it was going to get...' It cycles in the double-action mode, and seems to time, but I'm not sure.
I didn't buy it to shoot it much, but I'd like to get enough ammo through it to compare with other revolvers on a chronograph survey. I'll probably leave well enough alone and keep it on the shelf.
The all time 'worst' gun I ever owned was a 'Buffalo Scout' revolver; a single action .22 long rifle/.22 Winchester Rimfire Magnum made in West Germany by the same company later known as R. G. and Rohm. Timing was poor, lockup was worse and it broke triggers at all times.
I finally sold to a guy I didn't like.
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Best description of a bad trigger pull goes to Big Jim P, for his wonderful phrase: "...like trying to squeeze the head off a chicken..."
I laughed my fool head off at that one.