XM8: Polymer Cartridge Casings

[starfuryzeta]

http://www.strategypage.com//fyeo/howtomakewar/default.asp?target=htweap.htm

To further complicate matters, the army is also looking into what appears to be the first workable non-metallic cartridge case for rifle rounds. American form Natec, Inc, has developed a polymer based cartridge case that is easier, and cheaper, to make than the traditional brass ones, and weighs 25 percent less. This means that ammo would be about twenty percent lighter to carry. The lighter polymer cases also result in less propellant being needed, and thus less recoil. The Natec cartridges use the standard brass or aluminum base caps, primers, propellants and bullets. A round for the M-16 is available now, and a 7.62mm round will be available this Summer. The Natec cartridges are new developments and have not received much field use and testing yet.

What does the makeup of the case have to do with the amount of powder needed to propel the bullet?

 

[Third_Rail]

I hope that flops, I'd hate to see manufacturers switch to ????ty cases that won't hold up just because the military switched.

 

[Lightspeed]

I've got some of these!
They work really well.

 

[benEzra]

What does the makeup of the case have to do with the amount of powder needed to propel the bullet?

I can think of three possible reasons.

One--under reaction conditions of 1200 degrees fahrenheit and 50,000 psi, the polymer itself could be combustible. If this is true, only the case head would be ejected when the action cycles. (Lightspeed, does the polymer case burn up when fired, or is it ejected with the brass case head?)

Two--the polymer isn't combustible, but soaks up less heat from the burning gases than brass would, thereby leaving more energy in the combustion products to propel the bullet.

Three--the polymer serves as insulation between the combustion products and the chamber walls, reducing heat loss and thereby leaving more energy in the combustion products to propel the bullet.

 

[Third_Rail]

More than likely, it's the third. I still don't like the idea of polymer cases, though.

 

[Lightspeed]

Yeah, the case ejects just like a regular brass one.
It's not hot either, when it does, you can pick it right up. I guess this might have something to do with it having less powder. It shoots just like the Winchester white box ammo, and is just as accurate.

 

[MLC]

As if the millions of tons of other discard plastic littering the earth wasn't enough.

 

[SodiumBenzoate]

I hope that flops, I'd hate to see manufacturers switch to ????ty cases that won't hold up just because the military switched.

Yes, because polymer is so weak

I believe one of Cavalry Arms' telescoping polymer buttstocks took a bullet and the bullet deflecting down into the table it was sitting on, and the buttstock still worked fine.

As if the millions of tons of other discard plastic littering the earth wasn't enough.

Metal isn't exactly that much better.

 

[Master Blaster]

Metal isn't exactly that much better.

But you can reload metal, and you can melt it down and reuse it to make new cases.

Can you reload the polymer case???????

 

[Archie]

What does the makeup of the case have to do with the amount of powder needed to propel the bullet?

The polymer is also probably thicker than a conventional brass case. That means the inner burn chamber is smaller in volume. A small volume requires less propellant for the same pressure level.

I want to know if they can be reloaded without massive re-tooling on my part. Does the case mouth retain tension? What about crimp?

 

[Third_Rail]

Yes, because polymer is so weak

I never said it was, but try making a stock out of the same polymer as the cases are made of. There is more than one type, and I'd wager the cases are made from the least expensive type.

 

[George Hill]

Yeah, we all know how useless the idea is in shotgun shells.


If it means cheaper surplus ammunition on the marker - go for it. I'm not a reloader, so I don't care about that.

 

[clubsoda22]

the stuff will probably be so inexpensive when it turns up as surplus, you won't care about reloading it. Of the reviews i've read about this ammo, they have all been good. Different color plastic cases will also make it very easy to distinguish different loads.

 

[Vern Humphrey]

Not to be pickie, but sausatges have casINGS. Cartridges have cases.

 

[clubsoda22]

who are you talking to?

 

[Vern Humphrey]

Check the thread title:

XM8: Polymer Cartridge Casings

For a moment, I though it was all about making summer sausage.

 

[clubsoda22]

you are being pickie

 

[Vern Humphrey]

Reminds me of a Law and Order episode, where the bad guy was shooting people with a double-barrel shotgun.

The brilliant detectives decided that since there were no "casings" found at the scene, he had to be using a "breech loader."

Well, duh!

 

[Third_Rail]

Or... maybe a musket! Wow!

Right, anyway, I'm all for cheap surplus ammunition, but I'm also for reloading and custom match loading. I don't want to see brass cases go the way of brass hulls (i.e. really expensive and hard to get)

 

[natedog]

Just curious, I haven't really thought of this before, but why isn't brass standard for shotgun shells? Why has plastic (so far) been used only for shotguns and not rifles?

 

[Third_Rail]

Think of how BIG hulls for shotguns are. People don't like spending a lot of money on brass.
Now think of how tough brass is to work after a reloading. People don't like wasting a lot of time gluing wads over their shells, crimping the plastic is easier.
Now, think of how much easier it is to produce plastic hulls compared to brass.
Now, how about the average pressures of shotguns being fired? Not too much plastic is needed to make them safe...
It all boils down to saving money.

IMHO, these two aren't benefits when applied to rifle and pistol cases; I want to be able to reload, I want to have a nice firm crimp. For military use only, plastic is fine, but if the industry switches over and brass cases go away, I'll cry.

 

[Vern Humphrey]

Shotgun shells (and many early rifle shells) were made of paper with metalic heads. The advantages of paper were many -- low cost, ease of manufacture, and so on. The disadvantage was paper could swell in high humidity.

Brass shells require a different chamber -- since the interior diameter of a brass shell is larger than for a paper shell in the same gauge. The Army used all-brass shells in WWII in the tropics, but loading for guns originally chambered for paper shells was a probem.

The development of plastic shells overcame all the disadvantages of paper, and has proven an ideal solution.

If we were to go to all-brass shotgun shells, the interior dimension problem would affect performance, and we would gain nothing -- in fact, we'd lose in terms of cost, weather resistance and ruggedness.

 

[Preacherman]

Lightspeed, where did you get that ammo? Can the rest of us buy some? I'd like to put a few boxes through my rifles to get a feel for it, and see how well it works in various actions.

 

[Lightspeed]

I got mine from a friend who's a gun dealer, I don't know wherre it's for sale anywhere else.
I do have their web address, though=
www.natec-us.com/products.asp
Maybe you all can track some down from there!

 

[Onslaught]

I'm all for cheap surplus ammunition, but I'm also for reloading and custom match loading. I don't want to see brass cases go the way of brass hulls

So you don't want technology to move us forward and let the rest of us to have cheaper ammo just because it would inconvenience you?
(before you get offended, it was a joke)

Besides, if polymer cases are cheaper, then you could just buy THOSE and reload them... Just think, if they're really that inexpensive, you'd never have to resize brass again! Plus, if they use less powder, you're using less powder to reload, thereby offsetting any small increase in cost of the case itself.