Without rust??? :D
Good luck with that, they start to rust in the shop lol
Pressure test to 20% over pressure if you like but personally I'd just go with it as is
If it leaks then replace
Can't really advise on current models as I've not used for a while
All I will say is think about where you are going in the middle term ... obviously tech will change but good kit will still be accurate and serviceable for several years
Probably spending double what you expect ( no real idea...
It won't be come "a problem " until it has already happened... then the Bambi brigade will be screaming for their execution but some inkstain will have created a law making it impossible without using non lethal force
Another option might be to fit a sleeve up to the bullet then insert a drill into the sleeve...
appreciate the tolerance might be too tight at smaller sizes but if it's only a few inches then using a twist drill down the sleeve might be an option too?