How To: Fit The HAO L119A2 Ambi Mag Catch To A Marui MWS

So… I’m left handed. It’s at the very least an inconvenience and sometimes it’s a downright curse! Apparently we live shorter lives due to living in a world designed for right handed normies, on the other hand… We’re creative motherfuckers.

The MWS in action at Spartan CQB, mag changes need to be rapid when you’re up against high caps!

I’d count problem solving as not only one of my strengths, but a hobby. So when I bought the HAO Ambi Mag release (designed as part of their L119A2 kit), I wasn’t actually that annoyed about it not quite fitting. It’s a fantastically made little catch and I’m sure that in a PTW it’d drop right in without any work at all, I’m genuinely trying to make a square peg fit in a round hole by asking it to work with my GBBR.

I’ve had a similar (AEG specific) catch on my Marui Recoil for the last 3/4 years, it’s something that I’ve become so used to, that not having one on my Gas “rifle” feels like a big step backwards.

The AEG spec Ambi catch on my Recoil Shock.

So, the mod… how difficult is it and what do you need? Well it’s a piece of cake really, all you need is a Dremel rotary tool and something to make a 1.5mm shim out of. I’ve used a 3D printer to make mine, but you could easily make one from any scrap of plastic or metal sheet you have laying around.

The first step is to remove the original catch, once this has been done, you’ll see that if you fit a HAO Ambi mag release, it protrudes about 1.5mm too far into the magazine well. In order to counteract this difference, you’ll want to start making up the shim/spacer.

The spacer should fit snugly around the “axle” of the mag release and be of a uniform thickness. The reason for this is to ensure that it sits “square” and doesn’t become an issue in it’s own right. Making it fit snug around the axle will allow it to stay in place whilst the magazine release is being used and not rattle around.

You could always fit it to the receiver where the catch meets it, but the lubricated nature of GBBRs means that it’ll be a bastard to glue in place.

The “normal” side of the HAO catch

The shim I’ve made fits snugly around the axle, and follows the footprint of the flat section. You can make yours slightly too big, and then remove any excess material with a sharp blade by following the contours of the magazine catch itself. This should result in a 1.5mm thick spacer that doesn’t impede the travel of the magazine catch once it’s in place.

Test the fitment within your receiver and if it binds, you need to take off more material. Once it’s moving freely, assemble the Ambi catch, being sure to use its spring and button, not the original Marui one.

Sometimes it’s the small modifications make big differences.

With the lower removed from the Upper Receiver, you should find that this allows the MWS magazines to fit nicely in the magazine well, if your magazine catch still protrudes too far into the well, you need a little more thickness on your spacer. If the catch doesn’t engage on your magazine, you need to remove a little material from your spacer.

There is also the possibility that your catch isn’t adjusted correctly, so Now’s the time to ensure it is. The HAO Ambi catch has a grub screw on its inside face which allows for the angle of the catch to be adjusted, it’s vital that this is correctly adjusted, otherwise you could end up with magazines coming loose at the slightest touch or failing to drop free once the button is pressed.

The “catch” part of the release (1.) should fit flush within the two raised nubs.

Before we count our chickens and call it a day, those of you who slapped the upper back in place and fed a magazine into the well will have noticed that they don’t always engage the catch. The reason for this is that the MWS catch isn’t quite real spec, the real one is slightly taller and therefore you’ll need to look at a modification that’s a little more permanent.

Filing down the catch ever so slightly on its top face will allow the MWS’s magazines to fully lock into place every time, essential if you’re planning on actually using it. Just be careful to only take a very small amount off… You can always cut more off, it’s sticking it back on that’s a challenge.

See at the top of the ambi magazine release where I’ve ground down the catch, not much but just enough to make it work.

Once you’ve filed off enough material, you’ll notice how smoothly the mag release works. It should feel exactly the same as the original part, except for the obvious inclusion of the ambidextrous functionality. If it takes any more effort or feels any less smooth, you need to double check your spacer and catch angle adjustment.

The finished spacer, ready to fit. Note the grub screw in the centre of the catch, you’ll need some imperial Allen keys to adjust it though!

A final note, I’ve made mine from green PLA material. The reason for this is to show you guys what it looks like, and to ensure that I can actually photograph it (ever taken a photo of a black bit of plastic on a black bit of metal?). The other reason is that if something should fall into the inner workings of my MWS, I’ll spot the green bit far easier than the same item made in black… It’s also not visible from the outside so the colour itself really doesn’t matter.

Looking into the magazine well from the top of the receiver, note the tiny green spot to the left.

So there you have it, an ambidextrous magazine release for your MWS. In a few months it’ll probably be a moot point once the full HAO L119A2 kit is released for the MWS/ZET System platform, but until then or for those only wanting the functionality of the catch, this’ll sort you out.

Fitting L119A2 parts to non UKSF replica builds makes me happy

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