You will need an extra deep one for scoped rifles and a locking top for ammunition, the 6-7 gun size is really useful but costs around £ 280, however if you shop around you will get a new one for less or if you are really lucky secondhand even cheaper. If you are on a smaller budget start off with a secondhand 3 gun shotgun cabinet and put your rifle in sideways, cost £20 -£ 50 (you will need a separate compartment/safe for your bolt & ammo) but as others have said you will soon out grow it. Fix to solid masonry inside your house e.g. floor & supporting wall, in an accessable location and out of sight of visitors e.g. under stairs cupboard