This is a quick video tutorial on using the Combro CB625 to test the power of your air rifle.
The actual choice of pellet is personal to your barrel/gun combination, there is no one pellet that is perfect for all barrels. The best way to find your barrels favourite pellet is to try a number of different brands of pellets and see which gives you the best grouping, remembering to clean your barrel when swapping pellet types.

When using a chronograph to check your airgun is legal, make sure you use a pellet that gives the highest power/efficiency.

In regulated PCP air rifles pellets such as Bisley Magnums (10.5g) or JSB Exact Heavies (10.3g) in .177 or AA Field (16g) or JSB Exact (15.9g) in .22 are best for setting up and testing the power of your rifle.

It is your responsibility to ensure your airgun is below the legal limit with any commercially available pellet.
The limit in the UK for air rifles is 12ftlbs and 6ftlbs for pistols, any more than this and it is classed as a section 1 firearm (rifles) or section 5 firearm (pistols) and needs to be recorded on a firearms certificate.
Available direct from www.chronscopes.com and some retailers for around £40 delivered.