AR15 Receiver Mold Kit

[bedlamite]

It's also worth mentioning that AR lowers are normally  forged not cast. The two processes give you different characteristics. I'm not at all sure a cast aluminum lower would hold up well.

Essential Arms and Olympic sold lots of cast lowers years ago. some even had the happy switch, and as long as you don't use them to break down doors, they work fine.

[AJ Dual]

The main issue with casting Aluminum for precision, is you have to figure out a certain percentage for shrinkage.

Not a big deal if it's going to be machined and sized in all it's critical dimensions. However, if a DIY'er is trying to cast an Aluminum AR lower, and intends to do so with a level of precision that'll save him all the milling steps he's not otherwise capable of, like magwell, FCG pocket etc. and only have to do the drill-press steps, having a 3D printer to make your positive for the mold and scaling it accordingly is going to be important. 

[MechAg94]

I would think the polymer would take more abuse than cast aluminum (depending on the polymer).  Cast aluminum can be brittle stuff. 

[Hawkmoon]

It's also worth mentioning that AR lowers are normally  forged not cast. The two processes give you different characteristics. I'm not at all sure a cast aluminum lower would hold up well.

The original Olympic Arms "Plinker" model used a cast aluminum lower receiver. No problems with mine or the one a friend bought.

[freakazoid]

Might want to rethink using polymer lowers. They don't stand up to the flamethrower test. https://www.youtube.com/watch?v=GOWPtxUX-Us

[MechAg94]

The original Olympic Arms "Plinker" model used a cast aluminum lower receiver. No problems with mine or the one a friend bought.

I wasn't implying that it would be a problem in normal use.  Either one would likely work for what I use an AR for.  Just thinking the good polymer might hold up for more abuse than cast aluminum.  Where that line is crossed, I don't know. 

[KD5NRH]

You have to collect dross that comes to the top, but aluminium is surprisingly friendly to cast, even without flux.

MgCl/NaCl flux is available premixed at WalMart, (Morton's Lite Salt) so it never made sense not to use it when I was casting.

[Hawkmoon]

Might want to rethink using polymer lowers. They don't stand up to the flamethrower test. https://www.youtube.com/watch?v=GOWPtxUX-Us

Interestingly enough (or not, depending on your interests), neither does aluminum. A building inspector of my acquaintance once showed why aluminum skylights cannot (lawfully) be used in buildings whose construction type is classified as "noncombustible." It seems the test for noncombustibility involves exposing a sample of the material to some established temperature in a laboratory oven for a prescribed period of time.

Aluminum doesn't burn, but it melts at far below the prescribed test temperature and therefore can't pass the test. Which is why aluminum is difficult to weld, and basically impossible to solder.

[Fly320s]

Speaking of casting aluminum...https://www.youtube.com/watch?v=sEc5Jak9jsg

Some naughty words in it.

[erictank]

A brass lower and wood furniture. I would like that. 

Probably make Tactical heads go 'splody all over the place.  :)


bob

I can see that in my head.

It's a thing of beauty.

[MechAg94]

Interestingly enough (or not, depending on your interests), neither does aluminum. A building inspector of my acquaintance once showed why aluminum skylights cannot (lawfully) be used in buildings whose construction type is classified as "noncombustible." It seems the test for noncombustibility involves exposing a sample of the material to some established temperature in a laboratory oven for a prescribed period of time.

Aluminum doesn't burn, but it melts at far below the prescribed test temperature and therefore can't pass the test. Which is why aluminum is difficult to weld, and basically impossible to solder.

Aluminum will oxidize very easily in the right conditions.  In elevated oxygen environments, it will burn with great release of energy.  Of course, most things will burn with a high oxygen content. 

[Angel Eyes]

Might want to rethink using polymer lowers. They don't stand up to the flamethrower test. https://www.youtube.com/watch?v=GOWPtxUX-Us

Besides not being fireproof, the AR15Mold.com lowers don't appear to be reliable:

https://www.youtube.com/watch?v=D3Asb6Ou6ds    (part 1)

https://www.youtube.com/watch?v=yBkX1Bsq22Q     (part 2)

In part 2:

Bump fire fail at around the 8:09 mark.  Stress fracture near the rear takedown pin (10:08 mark in the video).

Magazine feed lip sheared off @ 10:52 mark.

In fairness, the polymer lowers appear to stand up to a variety of chemicals fairly well, except for acetone  (part 1).

[makattak]

I can see that in my head.

It's a thing of beauty.

I'm trying to work out how the stock should look.

I'm envisioning something like this, but without covering the brass. I really like the fore-end, here:



Obviously, there would need to be a wooden pistol grip, too.

[Angel Eyes]

One could even make a receiver out of wood, if so inclined:

http://www.weaponeer.net/forum/forum_posts.asp?TID=8035&PN=1&TPN=1

[BobR]

I am thinking more along these lines with a brass lower. That would be very nice.



bob

[Scout26]

And I've got a 5 gallon bucket of brass out in the garage....

[makattak]

And I've got a 5 gallon bucket of brass out in the garage....

I was going to claim dibs,  and then realized I have no means of melting it down and no time, either.

 :(

[RevDisk]

I mean if you melt it without inert gas, etc, you get a cookie that you can break with your bare hands.

And zinc is already a part of some aluminum alloys.  Pure aluminum is -really- soft, it's effectively never used

Na. What Nick said. In practice:

Melt scrap aluminum, haul off the dross, pour into a mold to make ingots.  Remelt again when you're doing a pour.
Muffin trays work great if you cook them enough to burn off coatings. Heat with a blow torch before pouring in molten friggin metals.
Use greensand with appropriate ratios.
Have two vent holes. One for pouring, one for air/overflow to escape. Your pour/escape vents should be offset. Even after skimming, any remaining dross gets stuck in this part. Hacksaw off the extra bits and the remaining aluminum should be pretty good to go.

You can use a graphite rod to introduce nitrogen, but not necessary unless you are going for a mirror finish. Even flux isn't necessary if you pour within 3-5 minutes of melt. Less is better. Some fluxes add corrosion problems. Because, well, it's salt. Non-corrosive fluxes are expensive or hazmat. Fluoride salts and/or cesium. "High temperatures" and "fluoride" are things that are awesome but only if you're downwind and have an independent air supply. If you have your mold ready to go before you melt your aluminum it's not an issue.  You may end up with some pinholes, but not many. Shrinkage is usually the large problem than fluxing or degassing.

It's not hard to find 'scrap' aluminum from metal shops of the alloy you want. Shavings or cutoffs. I prefer cutoffs, and easy enough to find on eBay.  I wouldn't use soda cans for an AR15, because of the vinyl and paint. You'd probably be fine, especially if you did an extra ingot stage. But you wouldn't be saving that much money and adding an unknown element.

[RevDisk]

And I've got a 5 gallon bucket of brass out in the garage....

How much do ya want for it?

[birdman]

Na. What Nick said. In practice:

Melt scrap aluminum, haul off the dross, pour into a mold to make ingots.  Remelt again when you're doing a pour.
Muffin trays work great if you cook them enough to burn off coatings. Heat with a blow torch before pouring in molten friggin metals.
Use greensand with appropriate ratios.
Have two vent holes. One for pouring, one for air/overflow to escape. Your pour/escape vents should be offset. Even after skimming, any remaining dross gets stuck in this part. Hacksaw off the extra bits and the remaining aluminum should be pretty good to go.

You can use a graphite rod to introduce nitrogen, but not necessary unless you are going for a mirror finish. Even flux isn't necessary if you pour within 3-5 minutes of melt. Less is better. Some fluxes add corrosion problems. Because, well, it's salt. Non-corrosive fluxes are expensive or hazmat. Fluoride salts and/or cesium. "High temperatures" and "fluoride" are things that are awesome but only if you're downwind and have an independent air supply. If you have your mold ready to go before you melt your aluminum it's not an issue.  You may end up with some pinholes, but not many. Shrinkage is usually the large problem than fluxing or degassing.

It's not hard to find 'scrap' aluminum from metal shops of the alloy you want. Shavings or cutoffs. I prefer cutoffs, and easy enough to find on eBay.  I wouldn't use soda cans for an AR15, because of the vinyl and paint. You'd probably be fine, especially if you did an extra ingot stage. But you wouldn't be saving that much money and adding an unknown element.

Too late, only 1 birdman was wrong point given out per topic.

[Fly320s]

How much do ya want for it?

Come get all you want for free.  It is currently stored at the Sig Sauer Academy in Epping, NH.  Sig doesn't require shooters to police brass so there is a metric long sh1t ton of brass on the ground there.  I have picked up all the 9mm and 5.56 that I can use for a few years.  I also scored a bunch of high dollar .308 match brass.  The local PDs and military guys don't want their brass, but I do.

[RevDisk]

Too late, only 1 birdman was wrong point given out per topic.

Na, not worried about the points, just sharing some casting info. I used to have one, building another one. I have a small forge already, and figured might as well get back into casting again. I know you're getting into welding, but if you need casting, lemme know. I'm buying a 5 gallon vacuum degassing chamber and with a furnace, should be able to cast pretty decent resin, brass, bronze and aluminum. That and the 'other stuff' is for the coffee table project. Yes, I know how "pants on head" stupid it is to spend hundreds of bucks on equipment for building a friggin coffee table when I could build another inlay marble thingie for a fraction of the cost.

Come get all you want for free.  It is currently stored at the Sig Sauer Academy in Epping, NH.  Sig doesn't require shooters to police brass so there is a metric long sh1t ton of brass on the ground there.  I have picked up all the 9mm and 5.56 that I can use for a few years.  I also scored a bunch of high dollar .308 match brass.  The local PDs and military guys don't want their brass, but I do.

I'll pay shipping?   

I do go to NH for vacation, but not going this year.

[BobR]

I'll pay shipping?

If the shipper were to flatten the brass out and stuff it into a large flat rate box (max 70 lbs) you could get quite a bit of brass into one I would bet.

bob

[Fly320s]

If the shipper were to flatten the brass out and stuff it into a large flat rate box (max 70 lbs) you could get quite a bit of brass into one I would bet.

bob

But would the value of the brass out weigh the cost of the shipping?

[BobR]

But would the value of the brass out weigh the cost of the shipping?

That's a good question. I think scrappers are paying around a dollar a pound for brass, I have no idea what it would sell for if you sold to someone other than a scrap yard. I guess it depends on whether or not the person really wanted the brass and would be willing to pay the shipping. At the very least it is a source of brass, which is sometimes hard to come by depending on location.

bob