Seems to be a common problem.
Mine done the same also.
I initially pulled the plastics off to expose the nut, and placed a shim between the nut and the frame.
It worked for a few bulbs, then failed again.
Took a hammer to the bottom of the frame, and bent it back in.
Not tried another bulb yet, but I suspect the frame is now weakened to a point it will just do it again
I think I have to take the blame though, as I suspect over-tightening the thumb screw is the reason for the damage
If you get the plastic cover off the bottom that the thumb screw goes through, all should become clear. Look at the bottom of the frame for it flaring out.
Andy
My PPK/S classic sadly did the same thing after tens of thousands of BBs. I managed to get it back into shape but eventually the same thing kept on coming back.
It was still shootable and I carried on shooting it until the barrel housing sheared away from the frame at which point it was binned.
It was a great little gun up until that point.
Great Deals with : Dave Dee, Dozy, Beaky, Mick & Tich
I need to take mine to bits again to familiarise myself again with how its set up. It was a while ago I bashed it back into shape
Rattling ideas round in my head, thought about replacing the nut with a piece of steel, then drill/tap for the thumb screw.
If memory serves me correct, I don't think it had a lot of space to do that ??
What about filling the void round the nut with something like liquid metal ??
I'm just thinking of ways to spread the load, so all the force is not pushed down on the nut, and consequentially bending the frame.
I'll strip it again and have a proper look when I get a moment. I'm sure the key is in distributing the load if I can see a way to do that.
Andy
It's not a thread issue; threads on both the nut and bolt are perfect. The bottom of the frame where the nut sits is distorted, so as you screw the piercing bolt up, the nut slips into the bent section of the frame, skewing the bulb out to the side. It's much easier to see than it is to explain
The South of England has 2 good things, the M1 and the A1. Both will take you to Yorkshire.