Is a lat move possible with an MG contract?

Always spell out accronyms to get good info. What is "MG"....I assume Machinegunner? Army Master Gunner? Former 0311 and former 0211.

The Marine Corps will always assign you based on the needs of the Corps, not on what you want to do. So...if you enlisted under contract that specifies two years as a Marine Guard and then three years as an 0311 Rifleman, then that's what it will be. The only way I can see you getting to lat move into your preferred MOS is if that MOS is so severely undermanned as to desperately need personnel. So check with your career planner to see whether that's the case with your preferred MOS. He can call HQMC and find out what's what. My guess is that if your target MOS is anywhere close to being balanced, you will be stuck with your contract.
I have a question: I've been retired a long time and admit that I don't keep up with MOSs in the Corps, but I recall that in my day MOSs like Guard Duty (Marine Barracks) and Marine Security Guard (Embassy Duty) were secondary MOSs awarded only for as long as a Marine was in the B-billet calling for them. After their tour of duty in the B-billet ended, the "guard" secondary MOS was terminated and the Marine went back to functioning in his primary MOS. Please update me how you got into an MOS as Marine Guard right out of boot camp. Is this some sort of recruiter scheme to linked to assignment to a FAST company that attracts young people into the Corps?