The House Appropriations Committee yesterday deferred action on $522 million to continue work on the MX missile project until after the administration decides how to deploy the system.

Appropriations' military construction subcommittee dropped the MX proposal from a $6.9 billion bill to fund military construction projects here and abroad, but the chairman, Rep. Bo Ginn (D-Ga.), said the action should not be construed as committee opposition to the expensive new weapons system.

There is considerable opposition to the original plan, hatched in the Carter administration, to spend more than $50 billion to shuttle a couple of hundred missiles around on a railroad track and keep potential enemies guessing where they are. Some of that opposition comes from western states, where the system would be located, and some from those who think it will turn out to be a useless expense.

Rep. Paul Simon (D-Ill.), a leading opponent of the original deployment plan, said he considered yesterday's deferral a significant indication that the Appropriations Committee realizes that House opposition to the original MX plan is mounting.

The committee also deferred action on $29 million for a disputed plan to buy 244,000 acres of land in southeastern Colorado to expand the Fort Carson tank training grounds. Ranchers object to losing their land, and environmentalists object to tanks rolling over the dry, fragile terrain where a jeep's tracks can still be seen 25 years after it drove across the range. Carson is an old cavalry fort left over from the Indian wars and, like the rest of the cavalry, was converted to tanks in World War II.