Making a MCS/Hydra receiver

[jdindadell]

This was a fun project, ended up being easier than I thought.

A little backstory 1st, as it will likely help with understanding why I did this, etc.

I bought a 7.62x39 AK mag-well from Wyndham Weaponry quite a few years ago. This mag-well is part of their MCS (multi caliber system) AR15 based platform, which is a licensed copy of the MGI Hydra. Basically it is AR15 lower receiver that is made to accept a variety of removable mag-wells to allow for caliber conversion. There is also an upper that allows for tool-less barrel changes, but I do not have that, and honestly do not think that it is anything more than a novelty (and the interchangeable mag-wells is not much different either if I am being honest!). My end goal was a AR in 7.62x39 that fed from AK mags. I like making stuff so the thought of modding an existing AR15 lower to work with the mag-well was appealing and I figured I would likely buy the AR15 magazine and colt 9mm magazine mag-wells at a later date.

Well, that later date came and went, Wyndham is out of business, so no more new mag-wells to buy. And I never did get the correct upper receiver either, which has to be wider at the magazine well area to accommodate an AK magazine, since they are wider across than a std AR15 magazine. So I did some more research, found that Gibbz Arms makes a purpose made upper that will fit the AK mags, has shelves that prevent over insertion, and has a non-reciprocating side charging handle on the left (correct) side of the receiver. That solved many issues, and got my interest back in this project.

On a side note, I also purchased a used, complete, Palmetto KS47 rifle, and a selection of 80 percent AK mag lowers from various companies that had become available since I originally started this project. So now I have multiple options, and the end result of this deep dive is likely beyond the scope of what I am showing here. But I know people like to see stuff built, so here we go. Pics and info to follow.

 

[jdindadell]

So here is where I started.

Gibbz arms upper with the MCS mag-well attached, a "project" cast AR15 lower that I had molested as part of a failed single shot 50 bmg project (i salvaged that project with a single shot lower from hellfire armory). I got a handful of these cast 80 percent lowers many years ago for cheap and have used them for prototyping and experiments. Maybe 20 bucks each, so no worries if I botched one up.

So I used the trusty hacksaw to remove the bulk of the un-needed material from the front of the receiver.

Then I setup the back half in the mill and leveled up the protruding areas to the side of the receiver.

this pic shows that the magwell will fit over the center section of the receiver. there is some slack side to side, but that will be taken up with the rail sections that need to be machined to fit.

 

[jdindadell]

Now the receiver will fit inside of the mag-well track, but is too long front to back to be able to be pinned to the upper correctly.

Here is a shot of the caliper showing the amount that needs to be removed from the "new" front of the receiver. This will allow the to piece to achieve the correct length to properly fit the upper.

So back into the mill so that I can remove the un-necessary material.

I decided to just carefully mill till the front face of the receiver was flat, then I could take it out of the mill, mock up and re-measure so that I could get the specs just right.

 

[jdindadell]

So I took it out and mocked it up. How does that old saying go, "better to be lucky than good"? Well I got lucky and it was just about spot on, about 15 thou shorter than it could be, but I did want some gap so the 2 pieces could slide apart. As this is a prototype I am happy and will know better next time I mill one to remove slightly less metal before the test fit.

Now that the 2 pieces are dimensioned front to back I need to measuer the gap between the track on the mag-well and the receiver. Note the feeler gauge, about 25 thou.

I dug around and found a sheet of AL that was very close to the target thickness, cut a small part and squared 2 sides so i could clamp it in the mill.

Then I milled a slot so that the leg of material was spot on correct for the width of the track on the mag-well. Made 2 of these, identical.

Cut the 2 legs off, then clamped those up and machined the thickness down to almost the needed dimension.

 

[jdindadell]

Once I had hand filed those pieces down to exact fit, I slid them in between the receiver and the track in the mag-well.

Used a clamp and a 15 thou feeler gauge to space the to halves correctly, and made sure the clamp would clear the inside of the Upper so i could pin the upper on to complete my correct setup.

I mixed up a very small amount of JB weld and used a tiny amount to stick the 2 pieces to the receiver, just slid them into place from the bottom.

 

[jdindadell]

The JB weld was allowed to dry overnight, then I carefully seperated the 2 halves. Good to go, so i drilled and tapped 2 holes on either side and installed set screws with some JB weld on the threads to lock it all together.

Last milling operation was to mill a small recess on the left side. This interfaces with the magazine catch, and holds the 2 halves together when the upper in not on. I have a decent fit, so they do not slide apart easily.

Still need to do some final clean up and polish, and some sort of coating. Ill update once that happens.

 

[T-boy]

Love seeing projects like this come together. Thanks for taking the time to document and sharing!

 

[SMR412]

Thanks for sharing, very cool!

 

[jdindadell]

I did some research and even though Wyndham is out of business, MGI does still sell guns and parts. The mag-wells are epic, like 275... So not sure if I will be "investing" in one.