how do i load weapons for single mission?

[SEE]

are you sure you have entereed your new and saved weapons into the right weapons 1 loction?

The above duplicates the same process as using FMB which updates the MIS file using your saved weapons loadout identified in the FMB Objects panel.

I have just (using the above method) added various weapons load outs to all the allied missions and all are working fine.

Which mission did you try to change? copy and paste it , see if I can help.