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Casted plastic ammunition?

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Casted plastic ammunition?

Unread postAuthor: FighterAce » Fri Jan 21, 2011 4:27 pm

I'd like to try and cast plastic ammunition but I don't know which plastic can melt at a low enough temperature and can be poured into molds. Any ideas?
It should obviously be able to withstand the launch and survive +600 fps. For stabilization I was thinking about a metal weight in the nose.
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Unread postAuthor: Gaderelguitarist » Fri Jan 21, 2011 4:37 pm

According to what I just read, Type 1 PVC melts at around 360 degrees Fahrenheit. In theory, this could be done in a conventional oven.

For reusable rounds, look into Polyethylene. It's an impact resistant plastic that Sureshot inc. uses for their rounds.

EDIT: Polyenylene won't pour though, as it does not technically melt. Your best bet would be to machine rounds from round stock.
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Unread postAuthor: Hotwired » Fri Jan 21, 2011 4:44 pm

Polycaprolactone is what I've used to make slugs.

You can't pour it in any meaningful sense, it's like very thick syrup when softened but you can mould it very well.

Goes by a variety of commercial names, in the UK it's generally Polymorph.

Both the launchers in my sig sport a moulded grip it but the second shows some stages in making it.
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Unread postAuthor: FighterAce » Fri Jan 21, 2011 5:00 pm

Gaderelguitarist wrote: Type 1 PVC melts at around 360 degrees Fahrenheit


Are you kidding? :D Whats way too much

Gaderelguitarist wrote:For reusable rounds, look into Polyethylene. It's an impact resistant plastic that Sureshot inc. uses for their rounds.


I'd rather use something biodegradable...

Gaderelguitarist wrote:Your best bet would be to machine rounds from round stock.


If I had a CNC lathe, it would be making those bullets right now and we wouldn't be having this conversation. I need it to pour because I'll be using RTV silicone rubber for the mold. I'm not sure how it will handle with the molten material being pushed into the mold... or how I will even push it in :lol: I don't know why but it sounds incredibly stupid...

@Hotwired
Did you ever try heating it up a bit more to see if it would flow? How did your slugs perform?
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Unread postAuthor: jagerbond » Fri Jan 21, 2011 5:03 pm

Check out Polytek products. Their polyurethane 2 part pours easy and hardens in a couple of minutes. The Pic is how we made the body of our prototype CR80 rounds. Once cured we fill the hollow area in the center with foam, add steel nose weight and over mold with 40 or 50 durometer rubber nose cap... also from polytek.

Mold release is key, I know from experience.
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Unread postAuthor: jrrdw » Fri Jan 21, 2011 5:15 pm

Injection Molding Machine. Don't quote me on that title but it's what my middle school wood shop teacher had and brought into class the last day of school and we took turns making our own screwdrivers. It was a table top model.

Feed plastic pellets into the top, waited like 5 minutes, placed the mold in a clamp, lowered the nipple, pulled a lever down until the plastic came out of the mold relief hole and let the mold cool then popped out a screwdriver.

Edit: This is what I'm talking about, upper right hand side.
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Unread postAuthor: Technician1002 » Fri Jan 21, 2011 5:48 pm

HDPE requires high pressure to mold it. It turns soft like melted cheese and doesn't pour into a mold. Only high pressure injection molding works with it.
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Unread postAuthor: FighterAce » Fri Jan 21, 2011 7:05 pm

HDPE also requires high temperature... all polyethylenes and polyamides do.
Polytek stuff is pretty expensive... not really worth making one time use projectiles out of that.

I'd love to be able to use polycaprolactone but the first challenge is to find the translation :D Online translators never work for poly... stuff.
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Unread postAuthor: Gaderelguitarist » Fri Jan 21, 2011 7:22 pm

Well if melting plastic in an oven is too much, then the two part casting route is probably the best bet. Use some cheap two part epoxy in your mold and that should do it.
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Unread postAuthor: FighterAce » Fri Jan 21, 2011 7:49 pm

Last time I checked there was a difference between 200°C and 60°C...

And why do you insist on the oven? You could use an electric stove and a metal container. It would be much more efficient.
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Unread postAuthor: Hotwired » Fri Jan 21, 2011 7:56 pm

FighterAce wrote:@Hotwired
Did you ever try heating it up a bit more to see if it would flow? How did your slugs perform?


Slugs are fine as long as you use softer targets, not firing into ground/sand or at excessive energy into solid targets because they will deform if they get crushed hard enough.

It's a low temperature plastic, melts at 60 degrees, you can mould it with your hands, ram it into short barrel sections to create slugs. But if you want detailed stuff you'd need to look at high pressure moulding. It's not a casting material.

As for the name, that's not usually its commercial name. If you can't find someone selling it you might be able to buy from say the UK where it's sold under the name of Polymorph.
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Unread postAuthor: metalmeltr » Fri Jan 21, 2011 8:49 pm

What about polyester resin, more commonly known as fiberglass resin.

Fiberglass Resin

Wax a peice of pipe the size of your barrel and cover the end in tape, fill with mixed resin. You can then grind a point on it. I have also casted bullets in the pointed form. It works but the tape doesnt always react well to the heat of the resin curing.
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Unread postAuthor: Gaderelguitarist » Fri Jan 21, 2011 10:00 pm

I only suggested an oven because most people have them.

Ideally you'd go for a plastic injection machine, or a two part resin. Resin won't require you to even think about melting things.
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Unread postAuthor: Gippeto » Sat Jan 22, 2011 1:52 am

Lowest cost (and easiest) option (around here...don't know in Croatia) would be the previously mentioned fibreglass resin.

The plastic ones in the pic are hdpe, made with an injection molder in the mold shown. 3/8" ball bearing tip on a couple of them.

Honest opinion? Too light, and not worth the effort. Did NOT survive when fired. Simple cast lead is easier, and works better.

Think I have some pics somewhere where I used a 1/2 ounce fishing sinker encased in the plastic in place of the ball bearing....those fit the bore well, and had enough mass to work nicely. :twisted:
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Unread postAuthor: jackssmirkingrevenge » Sat Jan 22, 2011 2:21 am

Gippeto wrote:Lowest cost (and easiest) option (around here...don't know in Croatia) would be the previously mentioned fibreglass resin.


That cast in a "foster slug" shape with a consistent metal weight dropped in the nose (say a ball bearing or a nut) should make for a damaging and accurate projectile that's relatively easy to mass produce - which would be an asset, considering that it's highly unlikely to be reusable if used against hard targets.
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