From old literature: In a spring piston airgun the pellet must remain in place at the breech taper until sufficient pressure builds to release/accelerate it toward the muzzle. Seating them past this point may reduce velocity and accuracy.http://www.arld1.com/images/swfs/pistonpelletdynamics.swf
Hi TerryA while back, when I owned a Nitrogen Piston thingy, I tried both ways - pushing the pellet as far as it would go using my finger; and I also used this pellet seating tool. I didn't seem to make a difference in accuracy.