Hide the mags of Gung n' Ammo and Readers Wives.
It will be quite relaxed i expect so don't worry. Questions may be effective range of weapon, ensuring you have a safe backstop, not shooting where you can't see, quarry id, house secutity (window locks, front door type and lock) but i doubt he'll bother. He'll just want to see that you're a sensible bloke... tidy up, get the kettle on and a pack of hob-nobs... jobs a goodun.