Plastic cased ammo

The military is seriously pursuing plastic case ammo so it obviously is feasible. You just need to find the right plastics. And a coating inside the casing like teflon or some other very durable polymer might protect it from the momentary extreme heat of firing the round. It only needs to survive the heat for like 0.01 seconds before the casing is being ejected from the gun.

>rounds cooking off, but literally and inside your chamber

Attached: ilovechicken-06_zpsfc314efb.jpg (712x538, 105K)

As long as your case doesn't fail during the actual firing, the heat build up is LESS with plastic cases. Less heat is transmitted through the case into the chamber wall because plastic is a better insulator than brass and so it remains trapped in the case and is ejected with it.

The "brass as a heatsink" thing is overblown anyway. Its because of people misunderstanding the primary cause of cookoffs in caseless rounds. Actual difference in heat voiding is like 5%. Oh no my rifle fires at 900rpm as opposed to 950! It's so ineffective now, it might as well be a bolt action!

No. but I'd love to see it

Attached: 1533397065881.jpg (280x158, 13K)

>children still don't understand heat sink and ductility

>doesn't understand basic thermodynamics
That's why you are arguing for a technology that will never succeed

lol

Because it's in the chamber too, where the bullet can't get to outside of a catastrophic failure.

Theoretically, could I 3D print cases? What would happen if they fail? Won't the explosion just be contained inside the chamber anyway?

>wanting to breathe in burning carcinogens like bisphenol-A and dioxin

Protect your ass, stick with brass.

Attached: 1528750592446.jpg (411x418, 43K)

Here's Alex C.'s video on the plastic ammo turning his magazine into a hand grenade.

youtube.com/watch?v=mCjNkbxHkEE&t=402s

Attached: 1501139199035.jpg (368x750, 87K)

Wew lad

This will be a blessing for all those cheap turn of the century rifles in unobtanium calibers.

.43 Spanish, .43 Egyptian, 11mm Mauser, the Werndl cartridges, some of those weird french calibers...

Yikes. What would be the outcome if a failure like that happened in a bolt-action rifle or pump shotgun?

Look at the results from LSAT, user. Less heat conducted to the chamber and cooler operation.

I have a bigass bag of polymer cased .38spl some guy gave me for free and it's fucking terrible. When I fire it I get tiny pieces of plastic shrapnel hitting my wrist and it's incredibly underpowered because anything more would cause bad things to happen.

So basically rifle and pistol rounds will end up like shotgun shells?

aluminum or brass base but plastic hulls? Is the black neck plastic as well or is that metal?

PCP plastic is shit.

Anybody who works with pcp piping for sprinklers and shit will tell you that stuff is brittle.

Those who want to use hot plastic for anything obviously haven't heated up plastic before.

>We're at a point where we can cast polymer receivers and 3d print them as well.
except we can't, they are at best poor single shot zip guns.

>Plus, part of the role of a metal casing is to carry heat out of the gun when it's ejected
eh, no the role of a brass casing is to expand and seal

>The military is seriously pursuing X so it's obviously feasible

no

The LSAT program is interesting and might bring about some significant development in firearms technology.

Polymer cased versions of existing ammunition is a bit less promising. It has been tried many different times and ways for different reasons. There were plastic shotgun shells (both rim and hull were plastic), plastic rifle training cartridges like that blue German DAG stuff and some thus far failed attempts to make full-pressure polymer cased versions of existing cartridges like 9mm, 5.56mm and .308 but so far that shit just doesn't work.

It'll be interesting to see if polymer technology from the LSAT project will be backwards compatible with older calibers designed around metal casings. If yes we might see a significant drop in ammo prices. If no, and polymer cased ammunition becomes the new standard then everything we have now will be relegated to legacy support.

Don't shotguns get plastic fouling?

Not much fouling.
Consider however that the pressures in a shotgun chamber are very low and getting at it to clean the fouling out is usually very easy.

No they don't, lol.

>part of the role of a metal casing is to carry heat out of the gun when it's ejected

Sounds false from a physics perspective. Most of the heat would be in the gas. That gas would be vented to the outside when case ejection happens. Brass can probably withstand more heat than plastics, however. I think that is where a heat problem would arise.

Yes actually.

>polymer receivers
I mean, 556 is much hire pressure than what a lower receiver would deal with.

>condescends about "basic thermodynamics"
>is himself wrong about basic thermodynamics
Go on, explain why your thermodynamics disagrees with actual test results in reality.

gunsandammo.com/ammo/true-velocitys-new-polymer-cased-ammunition/
google.com.au/amp/s/www.thefirearmblog.com/blog/2017/11/28/lsat-cased-telescoped-ammunition-problem-cookoff-brief-thougts-002-follow/amp/

It's very true dude. If you have taken a thermo class you can see the typically the most effective way to remove heat from a system is to move mass rather than just purely rely on convection and conduction. This is the major issue with caseless ammo, it was the big issue with the G11. The gun would have cook-offs because it wasn't ejecting significant amounts of heat as hot brass and it wasen't insulated from heat. Both contributed to overheating. They could never really get it to the point that it was viable for long drawn out firefights.

en.wikipedia.org/wiki/Heckler_&_Koch_G11#Ammunition_cook-off_and_shape

Not exactly. The G11's heat issue was in part from the internal mechanisim's only opening to the outside being the barrel. It had no means of venting. Furthermore, if you have taken a thermo class you would know that the most effective way to remove heat from a system is to purge the system, if the heat is in a gas or liquid, and then replace the medium. Semi and full autos do this to a limited degree by allowing gas to escape and mix with the atmosphere during ejection.

I imagine the LSAT has to worry about this a lot less because the nature of a chain fed gun means there's lots of scope for ventilation.

> The gun would have cook-offs because it wasn't ejecting significant amounts of heat as hot brass and it wasen't insulated from heat.
Heat rejection from the case is negligible. The propellant coming into direct contact with the chamber wall was the problem. Chamber wall was barely hotter than that of the brass cased ammunition.
>They could never really get it to the point that it was viable for long drawn out firefights.
This is completely wrong, by the end of development it was better than brass cased 5.56 at resisting cookoff. Switching to HMX based propellant solved the issue.
>g11 heat issue
The G11 didn't really have a heat issue in the way that it was melting barrels and blowing gas tunes like other guns. It was basically entirely confined to the cook off problems.
> the most effective way to remove heat from a system is to purge the system, if the heat is in a gas or liquid, and then replace the medium.
Which is removing thermal mass from the system just like he said isn't it?

>just like he said

He assumed the thermal mass would be primarily in the case. It would not be in the case. The gas is the heat. Getting rid of the gas will do more than removing a casing that has absorbed some of the heat from the gas. Both help, but probably not to the degree that the thermal properties of brass vs polymer make a much of a difference to when the rounds cook off. Polymer being less convective would actually make it more resistant to cook off, assuming the integrity of the case holds up.

>The [highly inefficient and retarded government] is seriously pursuing [insert anything here] so it obviously is feasible.

Hahahahaha

>Implying the private market could invent nuclear power or the internet

what about deformation from the firing pin and heat

The military is adopting the LSAT you retard

why not? other than government laws banning private research into nuclear power, why couldn't the private market do so?

The internet was not even close to wholly developed by government research. Xerox had a U.S. wide data network in the seventies which they eventually sold. It was developed entirely on their own patents parallel to ARPANET and a good portion of the technology used in the internet post 1990 is from the Xerox company data net.

Only reason nukes were government made is because they cordoned off everyone from the private sector interested in it to their own needs.
You’re a fucking idiot if you think any government RnD isn’t based on private contractors.

Its more complicated than that.
The same amount of heat is present no matter what materials are used. A brass case removes X amount of heat. If a plastic case is not capable of absorbing that X amount of heat, that heat still goes somewhere. It doesn't magically dissipate.

The heat starts in the case, user. It doesn't have to go anywhere. To get out and into the chamber wall in the first place, it has to conduct through the case and it can't do that effectively through an insulator like the polymers used and so its ejected with the case.
This isn't even a theoretical argument, this is what's observed with actual polymer cases and real life testing. See: What your talking about would only apply if the chamber was the source of the heat, and only way for the case to sequester heat was through conduction from the chamber wall. That is not the case.

one man's "thermodynamic magic" is another man's "improper system boundary"

t. engineer