Cut openings in the drywall large enough and in such position that the boxes can be properly secured to the studs. Then patch the drywall.

Don't give up on steel studs just yet.

There are a couple of devices that provide for very rigid mounting of boxes. Two manufacturers that I know of are Caddy and B-Line. The two items are a telescoping box support and a box mounting bracket (for 3 or 4 boxes, depending on stud spacing). Both items cost about $2 wholesale.

One other item that may help is an adjustable far side box support. The leg of this item will rest on the drywall on the other side of the partition an prevents the box from being pushed back. You might be able to use this item to support your exisitng boxes.

Here's web sites for the companies I mentioned
Caddy www.erico.com

B-line www.cooperbline.com

Tom,

do both of those solutions involve me cutting my rock to get access? i'm already painted. I was hoping for a fix that didnt involve me having to cut and retape.

I am wondering if you might be able to sneak a nut behind one or more of the holes to attach better (because, after all, those screws are only holding by the tiny thickness of the metal stud) or perhaps you could work a pop riveter in there, and rivet the box to the stud. Otherwise Tom O's idea sounds like the best bet unless you could perhaps glue the box in, say, with JB weld.

a last ditch effor might be for me to be pull the receptacle out and, if i can get the angle, screw from inside the side/back of the box into the stud. so screw inside out. (of course taping the receptacle up good so nothing can hit a screw inside the box.) If i could get a screw in from the side i'd be golden.

You can also put in the metal anchors that go behind the drywall and bend over into the box.
If the gaps around the box are more than 1/8 inch they need to be filled.

Here is one brand of the mounts.

Here is a link that might be useful: old work mounts

Windowguy,

The items I referred to are for new work, though the far side box support may work in your situation without doing much drywall damage.

Brickeyee that will ABSOLUTELY fix my problem.. you're a lifesaver.. and thanks to everybody else's ideas too!

I use plenty of those for old work instead of the screw type expanding 'old work boxes' ones.

You can get volume back from the loss in the typical 'clipped corner' design.

After cutting an box size hole in the wall (same size in drywall, 1/8 inch over in plaster) and fishing cables, you attach box clamps to the cable.
You need a few knocks in the opening to clear the screws holding a gangable box together, but keep it to the minimum.
I often use non gangable boxes to avoid this problem.

Removes the lock rings and thread the wires part way into the knockouts.

Slide the box into the opening while holding onto the wires.
Pull the cable clamps into position in the box and install the lock rings.

Brickeyee, a fellow AR15 enthusiast apparently, is right. We call those "Madison bars" and they will stop the box from pulling out.

I am surprised that no one recommended just pulling the existing new work boxes out and replacing them with old work boxes. I would think that's a much better fix than ripping out drywall and patching it afterwards as some have recommended.

I'm confused, is an 'old work' box the same as a remodel box, ie designed for a retrofit, and 'new work' for new construction or where the wall is not yet drywalled? It did occur to me that a remodel box would solve the issue most easily.

"Old work" or "remodel boxes" come in different flavors from various vendors.

Some are a pretty much full size devcie box with exanding screw 'wings' to anchor them (together with the top and bottom plaster wings).

Other old work boxes have a clipped upper and lower rear corners and internal box clamps. The clipped corners allow clearance for the cables when the box is pushed back into the wall.

There are probably some other hanging around, but those are the two I see most commonly.

Using "Madison", "Hold-It Box Supports", etc with a regular device box works well also if you know how to get the cables into the box after pushing it in the wall (see the post above).

The problem with simply replacing the loose boxes is getting the old one out.
You need to cut the fasteners holding it to the stud.
A sawzall with a longer blade can usually be worked in beside the box to either cut it free of a stud strap, or cut the fasteners holding it to the stud.
It does run the risk of damaging the drywall, and even nicking cables that may be tight to the stud with staples near the box.

It is often worth the effort in plaster walls since repairs are more difficult then drywall (AC cable is also more resistant to minor knocks than NM if the blade touches the cable).

To simply tighten up a box that is pulling out of the wall the 'Madison' type clamps work very well.
You need to be sure to bend them so they are snug against the inside wall of the box to prevent contact with the receptacle screws, but you can get rear wire receptacles (Cooper) that have covers over the screws.