The "Type 1" (ie. backwire) receptacles are clearly able to take four wires per side (see image below).

I can't comment on your "Type 2" because I can't recall ever seeing those before.

As you stated, the "back stab" ones are garbage. Avoid at all costs.

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But if you're having difficulty fitting the wirenuts in the box, you may have an over filled box. There are limits to the number of wires/devices vs box size. It isn't as simple as "if I can stuff it in there, it's good".

Yes, Greg, I did think I might have an over filled box. It is a standard metal box like the one shown below, on the right, with only one device and the wire nuts I mentioned. The real problems are: I made the wires longer than necessary, I used red wire nuts I already had (replaced them with the smaller, yellow ones which are for 12-10 Ga wire), and the necessary pigtails for the ground, plus the pigtails for the black and white wires (I didn't try to double up on the screws, which I will do for the next boxes in my series). The boxes are all installed, the BX cable run, and the finished wall installed and painted. All I have to do is install the receptacles.

I'm no expert on box fill, but I think if you are using standard depth boxes (2.5") and 12 gauge wire, then you are overfilling the box. Maybe an actual electrician will jump in here and clarify.

So, what do I do now? Undo the working boxes and replace with 4" square ones (I'd have to cut out some drywall)? Replace the wire with 14 Ga and replace the breaker with 15A (still requires drywall work)? Concentrate on the ones not yet installed?

That handibox on the right is clearly too small other than to terminate a single 14g circuit. Once you have to have another set of conductors leaving, the box is way to small.

This is a great lesson on box fill: http://ecmweb.com/code-basics/box-fill-calculations

The answer is what do you do now, is you put the right boxes in there.

I'm also confused what on earth you're doing. New wiring is not done with BX.

How many boxes do you have that have 3 cables coming into it? There can't be that many. I'd replace those ones with the 4" square boxes.

I imagine more of your boxes only have one cable in and one cable out. I think you could get away with using extra deep boxes for those, so swapping them out may be done without too much drywall damage.

I'm also curious about why you're using BX. I'm assuming you actually mean AC, but I can't think of why you'd be using that in a residential building. I hope you aren't working on a commercial building.

For 12 gauge wire I usually buy the largest single gang boxes I can find, which are 22 cu new work boxes. That give you quite a bit of space for a standard receptacle.

When I am using the box as both a junction point and for a receptacle I usually either switch to a dual gang box (about 40 cu in), or use a single gang plastic box with a "sidecar" that brings it up to about 30 cu. However, most of the metal boxes in your pictures are probably lower capacity

If you have three 12/2 cables coming into a single gang metal box, you have six conductors. My calculation is that this would be 2.25 x 6 = 13.5 for the conductors, plus 2 for the receptacle, plus 2.25 for the ground and 2.25 for the clamps, for a total of 20. You could legally use a 20 cu in box, but might find it hard to fit all the wiring if you are leaving more than about 6 inches for each incoming wire.

Bruce

Greg, after your message yesterday, I went to Home depot and took a picture of my "type 2" receptacle and include it below. I just wanted to know if I could put two wires under one screw, and a third under the other. I put one wire under each screw, so the third had to be connected with wire nuts.

Next time you can reduce (and hopefully eliminate) fill issues by using 4" square boxes. They are start at 1½" deep but deeper ones are available if you need the space.

If you are going to finish the walls, the top with a "mud ring." Various depths and single and double gang are available.

Or use a raised cover for unfinished walls. Various configurations are available for different devices in both single and double gang:

I'm not really sure why you're running armored cable, maybe local code requires it? If you happen to be in Chicagoland, typically you'd need to run metal conduit for new construction. Armored cable is usually only allowed in retrofit applications where it isn't practical to install conduit without ripping apart the wall.

Well, to me, it looks like your 'type 2' receptacle should be able to accept 2 wires for each screw plate. But again, it's kind of a moot argument if you had the right size boxes because then using the wirenuts and pigtails would fit fine.

And then you could just use the cheap residential receptacles instead of these more expensive ones. Personally, I like the cheaper ones better. The high end ones typically have a much stronger grip on the plugs that you put into them, which sounds like a good thing, but actually pushing the plugs in and pulling them out needs some extra force.

Greg, thanks again for your comments. I do like the extra force required to insert (and remove) plugs for the commercial variety. The extra cost is insignificant (I just bought a box of 10 20A "type 1" receptacles for about 20-some dollars.

Mike, your comment about Chicagoland is right, and that's where I formed my opinions. I have used some of the items you illustrate, but I've used the 4" boxes only where I want to have double duplex receptacles, using the ring shown in your middle illustration. I don't think my local code requires armored cable (although my builder did use it in some cases), but for exposed wiring in living quarters, I to think it is required.

Easier to wirenut your wires together and one extra pigtail to the side of the outlet. I also prefer the outlets that DONT have back wiring because the side screws are then solid instead of jiggling all over the place while you try to wire.

Easier to wirenut all your similar wires together and one extra pigtail to the side of the receptacle. The receptacle will fold back into the box easier, and the simple wire wrapped around the simple side screw will work as good as the fancy ones. (Unless you are using stranded wire) I use a lot of Tan wire nuts for this. (and split receptacles where 1/2 is ccontrolled by a switch)