Actually, it is the whole process.
When you degrease and wash the pellets, if you do it carefully, you will note that lead "sand" has ended up in the bottom of the tub you use for the washing.
This lead "dust" is made up of small particles that were adhered (with the lubricant) to the pellets you just washed.
If the small grain of lead was located in the outside of the pellet, chances are that it will fly off as soon as the pellet starts spinning. BUT if it is inside the skirt, then it remains there and provides a de-stabilizing mass that produces a force when the pellet spins. By using dish-soapy water to degrease and clean the pellets, these lead grains are removed from the pellets.
By swishing the pellets in a collander, they roll and rub. Not only amongst themselves, but against the collander itself. This removes slight "flashes" left over from the dies and the swageing process.
After all the cleaning and degreasing, the "pledging" of the pellets then does TWO important things:
1.- It "seals" the lead in the pellet. Pledged pellets do not leave as much lead in your fingers as unpledged pellets. We TESTED this using "D-Lead" tracer/indicator strips, so this is not just an assumption. It is a reality. Lead in your fingers can end up in your mouth and then it ends up in your brain. Since lead is a conductor, it simply short-circuits your brain waves. This disease is called "saturnism" and it can be alleged that it was the cause of the fall of the Roman Empire, but . . . we digress, back to airguns:
2.- It lubricates your bore and prevents the lead of the NEXT pellet from smearing into the bore. Using Pledge reduces the need for bore cleaning and reduces bore leading up to 1,100 fps MV.
Some bores like Pledge, other bores like other lubricant. Automotive silicon wax has been good in a few barrels, Kry-Tech in some others still, you need to find out what lubricant your barrel likes. It is my experience that barrels are lubricant specific, if they like a lubricant, it will be across the pellet board.
On the Slim Jim pump, what you look at that resembles a cartridge re-loading press is not the Slim-Jim. It is the Ram-Charger.
A Slim-Jim looks like a bycicle pump. Look at it here:
http://www.uttings.com/?Categories/Shooting/AirCartridge/Brocock/
Take care, keep well!
Un Abrazo!
Héctor