buy one
You will need to specify the use.
you can't
Try oiling of the gearbox.
There are air rifles and there are air guns. These are guns that use air or C02 to fire a BB or Pellet, not gunpowder. A DAISY RED RYDER BB Rifle would be considered an "air rifle." There are several companies that make air guns and air rifles. Gamo, Daisy, Crosman, and Umarex are a few of these companies.
An Air Rifle is either a BB rifle or a pellet rifle. It uses air or gas to propel the projectile.
Not designed for that type of improvement
I am a little confused by your question. Do you mean Webley air rifle. I know that Wembly makes scopes but I am unaware that they make air rifles. If you mean Webley then I need to know the condition and the model of the rifle to give an estimate of value.
A person can make the pump easier to operate on a Crosman 760 air rifle by applying oil to the seals. This will provide lubrication and improve the overall action of the weapon.
A sporter air rifle and what?
No
Are you asking how do you swap and air tank on an air rifle, or swap for and air rifle? In most air rifles you put it on safe and swap out the tank by unscrewing it and replacing it.
Not designed for this type of modificaiton.