SHS M4 receiver review

Yeah, SHS makes M4 receivers. I didn't know until recently either.

This receiver is available from ak2m4.co.uk for £40. It comes packaged in a simple cardboard box with a sheet of dense foam on either side. Nothing fancy, but definitely enough to protect the thing.

 There's a white super shooter logo on one side which I'm not really a fan of.   

I forgot to put the bolt release in, blue is from the gearbox I installed

In the box, you get the receiver along with a small bag containing the little bits like the magazine release, pins, and bolt catch. First thing I did was rack the charging handle, and something fell out:

This is the piece that the charging handle's return spring hooks onto. I noticed that the stock charging handle spring was too long (maybe it just got stretched over time in storage?), replacing it with a shorter spring (for those of you without springs lying around, cutting a few coils off the stock spring should also do the trick) allowed it to function.
If you add a lot of pressure to the right (tilting it clockwise slightly) it still doesn't really return properly, and if you're also pulling hard enough, you can end up pulling the charging handle out of the receiver. It just sort of snaps back in, although the return spring you were using is going to be dead (just cut a few coils off and reinstall it and you're fine though).

New spring installed, stock spring on the right

After that, pulling the charging handle flips the dust cover down and pulls the bolt cover back, allowing access to the hop unit.

The magazine release button and catch are threaded and have to be installed like a real one, unlike some airsoft replicas where there's an extra screw.

With that cleared up, I decided to throw some parts in it and make an M4.

  external parts list:
ZCI 7" handguard
G&G outer barrel, buffer tube, crane stock, grip, sights
ACM AFG
ZCI gearbox shell (+ trigger)
SHS super shooter receiver

The receiver is pretty light. Heavier than plastic, but judging by the weight, I don't think it's pot metal (zamak). Doesn't seem like it's going to break any time soon. 
  
The back part of the receiver had to be cut down for the buffer tube to fit, but that's specific to this buffer tube design as far as I know so it shouldn't be a problem for most people. The handguard screws on fine but the depth of the threads means that being completely tight doesn't line the handguard up properly- people have reported this problem on other receivers so it might just be the handguard's fault though.

It's also quite a bit lighter colored than most parts, more of a dark gray than black. After putting parts into the thing, the charging handle started acting funny again. The bolt cover would get stuck, especially if I was holding the rifle by the receiver. Holding the rifle by the foregrip made this problem much less likely to happen. The solution was to just slap the receiver and then the cover snaps forwards. However, the charging handle doesn't click back into its spot if this happens:

You can push it back into place though, so there doesn't seem to be any permanent damage. My "solution" to this was to treat it as releasing a bow string in archery- don't try and let go of the handle when it's pulled all the way back, just relax your fingers and keep pulling back and the force of it pulling forwards releases it for you. When I did this, the charging handle would return forward perfectly every time. Pretty fitting solution to the problem given that the super shooter logo is a guy with a bow.

The selector switch is a bit mushy- there's a noticeable click when using it but not enough resistance to actually keep the switch exactly in the right position unless you're gentle with it.

The finish on the receiver seems durable. Not just going to flake off, but it'll scratch off with extended use, especially on moving parts like the charging handle:

Mag compatibility wise, it worked flawlessly (when using a lonex hop unit) with asg flash mags, magpul green label pmags, and some ACM (dboys I think) hicap  . 
With lonex flash mags it'll feed, but the mag release button seems to get jammed and takes quite a lot of force to press. When you manage to press it though, the mag drops freely. Lonex pmag flash mags literally can't fit into the magwell though, too thick. 

tl;dr:
M4 receiver.
Pros:
-cheap
-good build quality other than the charging handle
Cons:
-finicky charging handle 
-slightly wobbly selector switch
-gray color won't blend with black parts perfectly
-not so great looking logo on the side 

At £40, I'd recommend it. SHS didn't go above and  beyond to make a perfect receiver at a price lower than everyone else, but they made a good product at a good price. The only real problem with it is the charging handle and I might've just gotten a lemon, the rest of my complaints are quite nitpick-y and expected at this sort of price.