The nickel silver H&S nozzles wear & become enlarged over time in part due to the fact that they are somewhat softer than the stainless steel needles. Stick a worn needle & nozzle together & compare them side by side with a new pair & it's surprising how much further the needle from the worn set protrudes through the nozzle. If the needle hasn't been damaged over the course, quite often a new nozzle alone will restore optimum performance.
Nozzle enlargement through wear is normal, but a few things that can cause premature wear on these nozzles (I'm not suggesting that any apply to you) is too much pressure on the back of the needle when holding things together to tighten the chuck nut, continually letting the trigger spring back causing the needle to slam into the nozzle & fitting a needle which has a build up of dried paint (Future is bad for this if not properly cleaned / removed) in the area of the needle seal - as your are sliding the needle forward to chuck it, the dried paint causes resistance at the seal, apply a bit more pressure, the needle frees & slams straight into the nozzle.
