If the original piston seal is not damaged and fits snugly in the compression tube it should be fine. It should take three to five pounds of force to move the piston with seal installed. A looser seal will yield more fps but it can also cause damage when the piston slams into the end of the compression tube. It also accelerates spring breakage. A too loose seal is far worse than a to tight seal. If your seal is too tight you can make it looser by turning it down, just don't go too far. Keep trying it for fit during the process, always lubricating the seal before insertion into the compression tube. Beware that a higher power spring will shorten the life of the cocking shoe. It can crack or break over time rendering the gun unable to be cocked.
Iím about to install the TbT guides and wondered what do you lube the outside of the Comp tube with and does anyone put moly on the cocking shoe and cocking arm pivot pin or just gun oil?
I use thin layer of clear Vortek grease on the outside of the compression tube. I use a very small amount of 70% moly grease on the cocking shoe and cocking pivots. I don't put any lube on the inside of the compression it itself, but I do put a very small amount of clear Vortek grease on the side of the piston seal and piston bearings. For reference, I am using a Vortek molybdium disulfied piston seal, so it tends to be self lubricating once installed.I am using TBT guides in my TX200, with a very thin coat of moly grease. I used a small brush to apply the Moly to the spring and guides. Then I wiped the excess off with a paper towel. You need very little moly if your TBT guides fit snugly on your spring. Your should have no vibration and torque, and less forward surge in your shot cycle. I think the recoil is a bit less. I have found that my FAC TX200 shoots best when I use the thin slip washer on the top hat, and not the thick slip washer.