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Old December 5, 2013, 06:33 AM   #1
308Gunsmith
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Polymer 308 ammo

They're at it again, making polymer casing ammonium. What do you think about it?
http://www.pcpammo.com/limited
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Old December 5, 2013, 07:41 AM   #2
kimbershot
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had some in 223 and had no problems. sold remaining supply to a friend and he did experience some case separation. i don't think that much progress in polymers has transpired in the last few years. i prefer brass.
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Old December 5, 2013, 10:41 AM   #3
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Just a couple of years ago I was involved on the periphery of a Spanish firm that purported to have developed a polymer recipe that permitted the entire case to be made of polymer, i.e. without the brass head featured on the PCP case.

I have not seen any of it on the commercial market, but both the Spaniard and is American liaison were more interested in military contracts.

I do not really know anything about polymers except that what can be done with them is interesting and absorbs the focus of some very smart people.

Last edited by zukiphile; December 5, 2013 at 11:35 AM.
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Old December 5, 2013, 11:58 AM   #4
Kimber84
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Polymer 308 ammo

What's the premise behind it? Cost I assume? Weight?
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Old December 5, 2013, 12:05 PM   #5
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They said that the big advantage was cost and accuracy.

I wanted some sent to me for testing, but I passed that task off to someone else in early 2012.

I have two conceptual problems with a polymer case. First, I still think of polymer as plastic, like milk jug, and don't intuitively accept that plastic can contain those pressures. Apparently I am wrong on that.

The other problem is one to which I never received a detailed explanation. Brass carries a lot of heat out of the rifle. We've all had hot brass go down the back of our shirts. If polymer doesn't have the capacity to absorb that heat and expel it from the rifle, won't a rifle on fully automatic overheat more quickly?
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Old December 7, 2013, 12:44 AM   #6
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Polymer 308 ammo

Zuk, I believe the heat carried by the brass is minimal. Yes the brass heats up, but there's just not enough brass there to carry a ton of heat away. Also, that brass conducts heat to the chamber before it is ejected. Polymer will act as an insulator to the chamber, and a small amount more heat will be passed down the barrel. It evens out pretty well I believe, though I may be proven wrong.


NOTE:
I have not shot poly rounds. In fact, this is the first I've heard of them. I have worked quite a bit with many ultra high temp polymers though.
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Old December 7, 2013, 09:59 AM   #7
yotesmoker
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I like it,in fact I like it so much I picked up 5 cases of it.I use it in my ruger scout without any problems.Its a great plinking,practice round.No recoil at all but it is LOUD.The stuff I have is that blue german practice rounds.Its good enough for beer cans at 50 yards.A load of fun.
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Old December 7, 2013, 10:22 AM   #8
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I don't think heat is a big factor in the brass. The main things it does is expand to prevent gas blowback with the additional benefit of keeping the wear from the flash of the powder from the chamber walls. I'm guessing since I don't anything about polymer that it could do the same thing.
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Old December 8, 2013, 05:46 PM   #9
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Yotesmoker says it doesent recoil much, are these polymer bullets always gonna be reduced power?
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Old December 9, 2013, 09:31 AM   #10
yotesmoker
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There is no recoil at all,period,but it is loud.It moves out above 3000fps and will take down a coyote at 50 yards.Its one of my favorite plinking and varmint rounds.
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Old December 9, 2013, 09:44 AM   #11
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is yotesmoker talking about the same things we are?
I believe you are talking about polymer BULLETS while this thread is about polymer CASINGS.
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Old December 10, 2013, 12:15 AM   #12
Willie Lowman
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I saw some of these poly cases in 5.56 a year or two ago.

One thing that stands out in my mind is a pic of one of these rounds fired in a HK 93. The polymer got into the chamber flutes and it was a horrible mess.
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Old December 11, 2013, 06:52 AM   #13
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I'm talking about the german practice round in. 308.Its a blue plastic or poly caseing with a 10 gr poly bullet.It moves out somewhere around 3000 fps.I got them from Wideners,they were 109.00 a case [1000 rds] google german blue rounds to see what I'm talking about.
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Old December 11, 2013, 09:06 AM   #14
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I hope it works or that a non-metallic cartridge can/will be developed soon. Most brass is wasted. And brass is an expensive commodity.
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Old December 11, 2013, 07:54 PM   #15
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yotesmoker. that's some interesting stuff. I have quite a bit of german ammo in 7.62x39 that was steel cased, polymer cored and copper jacketed and thought that the ammo you were describing was similar. not to hijack the thread but that stuff is interesting, cheaper per round than surplus x54R.
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Old December 15, 2013, 05:18 PM   #16
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polymer .308

I was invited to purchase some of their polymer .308 for evaluation.
It's loaded with a Sierra 168gr HPBT.
However if cheap is to be one of the selling features then they will have to work on that a lot.
They are pricing it at $40.00 per box of 20 rounds.
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Old December 16, 2013, 11:03 PM   #17
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Well, at least plastic at 3000fps is, I'm guessing, pretty frangible upon impact. So this might have more home defense potential than we give it credit for, since stabilization/accuracy at range are much lesser issues than over penetration (I'm sure 'tis still enough to mess up a guy )

What's that line about a bicyclist hitting your house at 1000mph? Seems apt here

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Old December 17, 2013, 08:18 AM   #18
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so howzabout some good pics of these new poly cased rounds?
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Old December 17, 2013, 08:57 AM   #19
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http://www.thefirearmblog.com/blog/2...ly-production/

It looks as if maybe the most heat-sensitive area (shoulder and above) has been converted to a higher/harder grade of plastic.

Older picture...


Last edited by spacecoast; December 17, 2013 at 09:07 AM.
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Old December 17, 2013, 09:06 AM   #20
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Quote:
I hope it works or that a non-metallic cartridge can/will be developed soon. Most brass is wasted. And brass is an expensive commodity.
I agree that it would be nice to have alternatives (competition is always good), but don't expect the cost of polymer-cased ammo to be significantly less than brass-cased ammo. Brass is expensive, but it can be re-used (thankfully) for reloading, which lowers the cost of much of our ammo to (for the time being) manageable levels. The higher the price of brass goes, the less of it will be wasted.
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Old December 17, 2013, 09:25 AM   #21
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Copper is quite expensive, and it is only going to get more so. Brass cases are by far preferable if you want to reload... but if reloading is not part of the plan, I am certainly open to other case materials.

Does anyone make aluminum cased rifle ammo? I have only seen pistol ammo in aluminum case, but I can't see why aluminum would not work at rifle pressure... ?

If they can get polymer to work, it has the potential to be much cheaper than brass... but perhaps not as cheap as aluminum.
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