If I can get the ball bearing and spring to stay in place with a small cold chisel making the original cold headed marks a bit bigger there is always the issue of the whole assembly still being loose on the end of the barrel. Will locktite work?
I have tried to peen over the metal (using a small pin punch, not a cold chisel) but it was never successful as the material used for the front sight/underlever retainer is cast from something which I think might be known as "monkey metal". My solution was to bore out the casting and fit a brass insert to retain the spring and ballbearing. Fairly straightforward if you have access to a lathe. Loctite will hold it all together.