M120/M121 mortar ... what's the matter with my mortar?

Lubrication--Of course, you need to follow the lubrication chart on Page 3-4 in TM 9-1015-250-10. But remember when you squirt grease in the crank handles for the traversing, elevation, and cross leveling assemblies, more is not better. If you squirt and squirt grease in the handles, they can become difficult to turn. Give the handles a couple of squirts each and work the handles all the way in and out to spread the grease. Do that weekly.

Test the buffer--If the buffer binds, the mortar jumps more and that can hurt accuracy. Pull down the buffer as far as possible using the two housing tubes as handholds. Let it go. It the buffer doesn't smoothly return to its original position, something is wrong. Tell your armorer.

In the desert, don't lube all the unpainted surfaces of the bipod with GPL, even though Page 3-2 says to. Corrosion is not the problem in the desert, it's sand. Lube will attract sand, which will chew up the bipod's moving parts and seals. Wipe off all lube from the outside of the bipod in the desert.

Fully screw in the firing pin bushing--After you take apart the breech to clean it with dry cleaning solvent, remember to screw in the firing pin like it says on Page 3-27 when you put the breech back together:

Tighten the bushing hand tight. Then put on the mortar's socket wrench and give the wrench handle one hand tap to fully tighten the bushing. If the bushing is loose, it can ride up above the firing pin. Then the round won't ignite.