The recoilless mortar system (RMS6-L) on your M1252 Stryker mortar carrier needs a lot of care so it can keep throwing rounds down range.
One thing you do that the current TM doesn’t mention is removing the 120mm mortar tube from the recoil inner sleeve during monthly PMCS.
Once you’ve removed the cannon tube, clean the inner sleeve and remove any corrosion with a crocus cloth. Then coat the inside of the inner sleeve with a light coat of general purpose lubricant.
Be sure to wipe down the outside of the cannon tube and inspect for damage, including corrosion. Then coat the outside of the cannon tube with a light film of general purpose lubricant before reinstalling it in the recoil inner sleeve.
These steps will be added to the next revision of TM 9-2355-363-13&P (Sep 16).