Is it normal for a little air

[Justin]

Hi chaps, so I've just put my rapid back together again and all is now good after getting all my parts from Dr bob, however ive noticed a little air coming out of the grub screw hole that keeps the valve stem in place when I pull the trigger and have my finger over the grub screw hole. Is this normal for a little air to escape or should nothing be coming out of it? The grub screw is nip tight

[Squinty]

 it's common but shouldn't happen, some PTFE tape will stop it.
Don't tighten the grub screw down, screw in until it stops and back off 1/2 turn.

[Justin]

Appreciate the advice squinty. I'll have a look at weekend 

[Justin]

Should it be something to worry about performance wise ? Sorry for a thousand questions I'm terrible with the forum stuff lol.

[Squinty]

might cause some inconsistent velocities, slight drop in output.

[angrybear]

If it's air tight when left standing, but leaks on firing it must be air from inside the valve port,
you could try a smear of O ring grease around the outside of the fat part of the valve, before you fit it, that might be just enough to seal it.

[Justin]

Hi lads, just a quick update to let you know I now have my gun back and ready for some more ratting after a month of frustration. Took the rapid to John at Caunton gun supplies Newark who sorted the leaking exhaust valve hole by putting in a new M5 grub screw and giving it a slight De tune, what a top bloke. Thanks to everyone for the advice it's much appreciated