Simple questions sometimes require more than a "simple" answer.
You didn't need to delete your response, now I'll have to change mine since it makes for strange reading!
He didn't ask for advice either, but mine would be to shoot the 4" for a while and decide if the probably $200 or more cost to change the barrel would be worth it. Better to just buy another luger with a 6" barrel. JMHO.
While Lugerman has it would be the time to have the barrel changed, again JMHO.