Hi,
Also, if you shorten the barrel at all from the muzzle, you will remove the choke constriction that gives your rifle that great accuracy.
And as for shortening from the breech end, that's a job for the factory or those that do such work for a profession, and it won't be cheap.
You're best to leave the barrel well alone mate and buy that reflex type Airstream mk4 mod like Tony D recommends.