If you are suffering from a leaky grenade, struggling to hold gas or just a slow weep and fresh oil isn't fixing your issue, then it's time to replace its part.
 
This very affordable set, consisting of a full kit, can fully refurbish your 40mm Grenade from Nuprol. Make sure to lubricate every component before assemble and to do so after maybe 4 or 5 shots as the gas will freeze and dry out any applied lubricant.