I have an 9mm upper and I believe that it comes with some special FCG too. The sheet metal is 1.5mm ... whatever gage that translates to.

 
In case anyone is interested in trying to make your own, that translates to 16GA sheet metal.

This is beyond awesome

More people coming out of the shadows and making/ testing would be great. To see what works and what does not. I have few more of reinforcements left over if someone has a mold and means.

Finally a week later had the time to work on repairing my second mold.  Trimmed the grip screw threads off completely to make the central piece of the mold easier to reinsert into the template receiver.  After having reinserted it, I dribbled Mold Star into the safety plunger and grip screw holes, then reassembled the rest of the mold and left it all in the mold box overnight to set.  Had planned to use a syringe to remold these voids, but the one I tried couldn't handle the viscosity of the Mold Star 30, so in the end, I ladled it on with a spoon (and made quite a mess on my drop cloth).  I'd initially thought that entrapped air would prevent the grip screw from molding correctly, but my fears were unfounded.  When I pulled the mold, both plunger and screw holes had molded fully, and the plunger separated cleanly from the central piece of the mold this time.

Also took the opportunity to fill in some bubbles which had formed in the bolt stop and magazine release channels in the initial molding, and it looks like these mostly (though not completely) cleaned up.  Should have less obnoxious urethane bubbling to clear out of these spots in my next casting (which is currently in the mold).

A poster who PM-ed me (I won't say who in case they don't want their name used, but if they do, please pipe up and take credit!) had an idea which I like quite a lot: to insure all of the plugs for holes in the receiver center are molded as part of the outer pieces of the mold, simply tape over these holes on the inside of the receiver being molded.  The result should be clean mold separation and thin flashings on the resulting castings.  My only concern is entrapped air, so I'd probably leave the trigger guard open.  Actually, any bubbles which form should be straightforward to fill later simply by pouring a little more Mold Star into the receiver after it's been demolded and inserting only the central mold section until the new Mold Star has set and bonded to the old (which is a neat property you can tell from my posts I've been relying on heavily to fix my mistakes!).

Had planned to try this trick and tape off the holes for my repairs to this mold, but had two problems, both, as usual, of my own making:

• I failed to trim the tape correctly, with the result it kept kinking when I tried to apply it.


• In an especially moronic move, I'd already applied the mold release before I tried to get tape to stick, so it wouldn't.

In the end, I abandoned the tape and proceeded conventionally.  I do plan to try the tape in the next mold I make.  To minimize flashings thickening the whole interior of the receiver, I will try to tape only the holes and very slightly around them.

Since the Smooth Cast 325 I'm using seems to take far longer to set than given by the specifications, I will leave the latest casting in the mold for six hours or so.  I'm cautiously optimistic this casting will be closer than the last to where I want it to be.

This.  What's the best source online of these products for now?  My kids won't mind if I borrow some legos.

The basics Boris laid out are Smooth-On Mold Star 30 for the mold and Smooth-On Smooth Cast 300 for the urethane (I've been using 300 instead and have some regrets about that).  Other molding silicones and casting urethanes could be used, but you probably want to stick close to the Shore ratings Boris gives when you're first starting out (Boris discusses materials in first several pages of the thread and again later).  So far I think the only people who've posted their experience are following Boris' lead and using products from Smooth-On.  Smooth-On has local dealers in many areas but also sells over the internet.  They seem to keep a close clamp on their vendor pricing, so I don't think where you buy matters much to the price.

Can't say this enough, but read and reread every post Boris has made, and then you'll probably want to read my posts as well, because I'm coming up with all sorts of mistakes you should learn from.

Gotcha.  I've read the whole thread and seen you posts.  And would certainly reread before as I build legos and before pouring.

I called the local hobby store but they're on vacation and then the other go to vendor is Amazon but wanted to see where else I should be looking to purchase

Optimism is my most consistent character flaw.

Two steps forward, numerous steps back:

• The bolt-release slot is now clear of plastic blobs.


• The magazine release button is also now clear.

BUT

• The grip screw hole didn't cast straight.


• The safety plunger hole didn't cast straight.


• The magazine release hole was accidentally remolded when I fixed the button and now angles downward towards the left side of the receiver.


• The magazine slot in the magwell has become partially blocked.


• Something caused the top of the mold to rise, so when I pulled the casting, the bottom of the receiver was a giant flashing

Clearly I need to do more repairs and remolding.  I may start from scratch with a new mold, or I may simply cut out large parts of this one all the way to the surface and remold those areas.

Also, Smooth Cast 325 takes exceptionally long to harden. After 6 hours it was hard enough to demold but still easily deformable.

Somewhat discouraging results all-in-all, though as always I have more information about what works and what doesn't.

Thanks for the updates.

I won't have any play money until next month but seeing your problems will sure help when I can get started.

I think I will try molding the mag well and the fire control seperately.

Use aluminum tape to seal the top and bottom of the reciever and clay and tape on the outside of the holes.

Then use clay to form up half of the outside and pour one side at a time.

I have looked at and turned the reciever until is almost worn out from handling.

Good luck to you and keep posting . I need all the help I can get.

Frank

 


If anyone wants to see it I can either email it or post it here....or when I get around to making mine I'll just post pics.

 
I would honestly try nipping off the plunger tube holes as well as the grip screw hole.  Just leave them as "dimples" so you can drill them out with a drill press or by hand.  Add a helicoil or try to tap the plastic.  


I would probably lean towards tossing the mold out though...I could just see the dimensions getting all wacky with the attempts at fixing the mold, and that'll cause even bigger frustrations later when you go to put parts in and nothing lines up.  

I thought about using tape on the inside but was concerned the tape would leave a ridge in the casting.
Thought about using clay in the holes with tape on the outside if I can find out what kind of clay to use.
Then use foam board after laying reciever on it's side lined half way up with clay to make the box.
Frank

ETA. Boris, could you post the template you used to cut out the template for the brace?

 
Frank, send me a PM with your email.  I'll send you what I sent Sample.


If you are doing Boris's method and you want to use tape it, you MUST put it on the outside of the receiver.  And yes it will leave a ridge.  For clay you want to use Non-sulfer art clay.  I'm not quite sure what you're trying to say with the last sentence.

One difficulty I'm having with the repairs is that I'm actually using the original receiver, in-place, while I perform them.  That should mean in the end they come out right, but the trade-off is that every repair is a little geometry problem of its own.

On the other hand, I'm not quite sure what went wrong with the magazine release.  That experience would seem to discredit my thought that working with the original receiver inside the mold would be the way to go about the repairs.

If anyone needs pictures hosted, drop me an IM.

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This is what I've found. The product names are buried in the middle of the thread somewhere.

If these aren't right, someone (Boris?) please correct me.

mold rubber-

http://www.amazon.com/dp/B00ETAY8RI/ref%3Dwl_it_dp_o_pC_nS_ttl?_encoding=UTF8&tag=vglnk-c102-20

casting plastic-

http://www.amazon.com/dp/B004BN7G0E/ref%3Dwl_it_dp_o_pC_nS_ttl?_encoding=UTF8&tag=vglnk-c102-20

tinting dye-

http://www.amazon.com/dp/B005ZSGQBO/ref=wl_it_dp_o_pC_nS_ttl?_encoding=UTF8&colid=1O15IFSO261E8&coliid=I3OLRFHI1LSGH5

That's why people (well me at least) are a little confused about the plastic/mold sourcing.  In the OP it was stated that it was running $30 for the mold and a couple bucks per lower.  The startup/trial costs are higher than initially expected.  

Still freaking cool though.  

OP has much experience in casting.  $30 is all it costs him.  He didn't count, nor did he show, all his failures.  If he showed you his $2000 of failed molds and his $500 of distorted, grotesque lowers, no one would try it.  

$30 of molding rubber if you buy it at the price per volume you get with the gallon size. . If buying starter kits, buy two of the silicone rubber.  For the urethane, one starter kit should make you a number of receivers.

If you - like me - are a novice at molding and casting, you might be better off with the gallon of silicone, but the cost of that is obviously a more substantial commitment.  

This is pretty cool. I didnt read all 13 pages but someone should try this. Thermochromic pigment

Can you get this silicone material in a high temp formula and cast your own suppressor covers?

i wouldn't for a number of reasons

Maybe something here you could adapt for your project?

fosscadboltar15lowerreceiver

This is along the lines of why I want to get one of those metal reinforcement pieces.

I've got a model I've been working on, that I much prefer to those currently on fosscad. I want to alter my design to incorporate the metal reinforcement collar.

i like the capitalist legos lol. you could use this mold to make wax casting then slurry coat that then bake out wax and cast with any metal you can melt.

so awesome, thanks for sharing boris!

First of all I would like to give a giant shout out to Boris, amazing work!  I am a complete noob to plastic resin casting, before reading this thread I didn't even know that it was something that I could ever so at home. I am however no noob to plastic guns, I am also know as FOSSCAD FP,  I have 3D printed a good two dozen lowers and many other firearm related parts. It's time to combine the tech for the greater good! #MOARGUNS

First step, print a lower. I went with the JT Vanguard and made some small changes to suit my needs, I got rid of the bolt catch and shortened the buffer tower.


Lower cleaned up and ready for the mold


Lower suspended in my box by some thin wire.


My mold took two entire trial kits of silicone, it isn't very efficient. The lower started to float so I dropped a chunk of metal on top to push it back down. That's gonna leave a mark :(


This might just work!



Oh yeah!


My  first pour, nothing to color them with at this point


It worked! Everything fits great.





Over the past  week many more lowers have been cast. :D


Ladies

I just finished my new mold box and plan on making a mold for the WarFairy Hermes lower soon.

FP3D, welcome!  Thank you very much for posting.  Very impressive results, and great to see interest in the 3D printing crowd too.  Your first try is a lot better than my second try was.    (My third try has been pending for want of time but may happen this weekend.)

Thank You! Your advise on cutting the mold was very useful, no idea if I would have cut the mag release on the right side otherwise. I noticed you were using Smooth-on 325, that stuff was a pain in the ass. From what I can tell it is impossible to get clear without a vacuum chamber and/or pressure. I've had good luck with smooth-on 300, 305, and some SRC RP-40 that I picked up off Ebay.

Most Awesome!

Retro lowers can be cast as well...

Albeit they'll be too weak for retro bayonet drill.  

I haven't had a chance to get out and shoot with a resin cast lower yet so I did the next best thing, violently destroyed them.
[youtube]https://youtu.be/X39arwrG5r8[/youtube]

https://www.youtube.com/watch?v=X39arwrG5r8

I've been working on that third mold since the weekend, testing if I can use MoldStar's self-melding abilities to eliminate air bubbles in the mold by pouring the mold in stages.  (Previous molds have all formed bubbles in unfortunate places, which are then filled with resin when cast.)  If this experiment works, I'll report on it thoroughly later, but in the meantime I thought I'd mention another trick which does seem to work well:

For this mold, I covered the rollmarks with a piece of packing tape rather than filling them with modeling clay.  This part of the mold seemed to work as well as the clay without creating nearly the mess.  If I were starting from scratch, I'd pick a receiver with an integral trigger guard, tape over the rollmarks, and skip the modeling clay altogether.

Boris, that opportunity you were waiting for has presented itself:

http://www.ar15.com/forums/t_1_5/1777866_.html

How many "operable" evil baby killing assault rifles can you make by Saturday?  

Round 2

This time I am molding a WarFairy Hermes lower that I slightly modified to suit my needs.



This time I have it securely mounted so it won't start to float around in the silicone, I also added vent holes and a channel at the front so I can pour the resin in from the bottom.





Ready to cut open




The new mold came out quite nicely!



First fill with resin, using Smoothcast 305.



Everything fits perfectly

I'm glad you did this. I had printed out a lower specifically for this, a Hermes that I had modified. But I've been TDY the past two weeks.

Watching the above video, what I might try doing now instead of casting:10-15% infill using rectilinear patterning. Drill acouple holes and fill the printed mold with resin. Then the same thing again, but filling with hot glue. Then maybe a version with one of the various JB Weld style epoxies.

this thread is awesome...and now I am going to have to try something like this...I bet using the plastic lower for a dedicated 22lr/.17/ or 22tcm would last a lot longer or even a 9mm build...

9x19mm blowback might actually increase stress on the lower.  It may be possible, however, to cast a 9x19mm blowback upper, as you wouldn't have the heat of the gas tube.

A couple more receivers from the new mold.

Can't you just print a mold?

It's been talked about but I really don't think that it would work that well. Just for example, how are the buffer tube threads going to work? That's just one part of it, you would need a bunch of sections that perfectly seal together.

3rd mold came out fairly well save for two problems, with one of them being yet another showstopper.  The first problem, rather minor, was a bad mold separation around the trigger slot of the receiver.  I had taped the receiver on the inside at that point, but next time I think I would try taping the outside.

The larger problem is that the grip screw threads, which I had taped off of the inside of the fire control cavity and reinforced with bristles from a steel brush broke off inside the threaded part of the receiver.  The bristles were evidently too strong and too short.  Perhaps they would have worked better had I filled a small portion of the threads with silicone and let it set before adding the bristles and repouring.

I had previously experimented with a machine screw to see if it could be used for the grip screw threads but stripped the head when trying to extract it from a urethane test casting.  I may try using a bolt, which has worked well for Boris and K1.

Pouring the difficult sections of the mold bit by bit did work well, as did filling empty volume in the main pour with spare silicone scraps from earlier molds.

Yes, you can.

Someone has suggested this material:

http://www.smooth-on.com/castable-expoxy-res/c1295_1374/index.html



Opinions?

Better have a vac chamber.

Fascinating thread!

Has anyone considered using melted Pmag plastic for the fill? Seems like it would be durable, but I know nothing of this.