First is it a rifle or carbine?
Two different springs and buffers.
Rifle. That is why I specified the Geissele spring and H1 buffer above.
What type of grease and how to apply?
Read your link, it's for carbine buffer tubes. If you have a rifle with a fixed stock on it as the SP1 came with, you will need a rifle buffer and spring which is completely different than any carbine buffer or spring.
The rifle buffer is longer and heavier than the H1 buffer and the spring while being longer has a softer spring rate.
To be clearer, the link is referring to gas systems not stock systems. The SP1 came in a rifle version and a carbine version, rifle = fixed stock, carbine = adjustable stock.
