well, that's not realy good

this is the so called "Sperrfeder" or lock spring, a very common element on dreyse guns in this time.

I would look for a professional tig welder this technology had make surprising progress in the last time and they are close to weld everything now in every way. I think its possible to weld the spring and it still have the orignal tension after. if it works its possible to weld the hole also when you have fix the spring.
interesting what it would make if you patch the bullet. seems some of the pressure blow by because of the lose fit.
imho the orignal muzzle velocity must have been higher than this because of the big primer pill so this lady rifle was not a toy.