I got this Paslode F350S framing nailer for free because it's not working. The sleeve was gritty feeling and then I accidentally ruined it while cleaning. The sleeve seal was cracked and brittle and the post bumper was destroyed. I replaced all Orings, just to be on the safe side. See links below for the parts and tools I used:

ORing Kit & Sleeve Seal (402011):
https://amzn.to/44GaPvo (affiliate*)

Post Bumper (500453):
https://amzn.to/3Z0wrS2 (affiliate*)

Snap Ring Pliers:
https://amzn.to/3eHsQ5l (affiliate*)

*Purchasing from these Amazon affiliate links earns my channel a small commission. Think of it as a tip that doesn't cost you anything. Thanks for the support!