Fwb 124/ Williams fp-ag sight question

As the title states, I have a beeman peep sight on my 124, which is the Williams fp-ag peep. I wanted to replace the elevation set screw with a knurled Gibbs screw but what I bought from brownells is too long. It’s the correct thread and supposedly the right part but it hits the rifles tube before it locks the sight. Any ideas what part I need?

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