This is a rather interesting article about the potential military use of plastic-cased ammunition.
A company that I had never heard of, True Velocity, makes it. Has anyone seen this stuff?
I can see that a 30% weight reduction is a big deal for the military, but I don't know as it is for the rest of us.
If we have to march off into the next world, let us walk there on the bodies of our enemies.
That is a rather poorly written article but the true velocity stuff has been around for a bit. Polymer cased ammo has little practical use on the civilian market other than perhaps commodity conservation but I would also imagine that polymer cases will not be as reusable for the reloaders so that might be a moot point.... The reason for the .308 round being first to market has more to do with that being the same general round as the M240 machine gun and its linked ammo being the heaviest stuff typically carried ammo wise by a infantry squad....Since we are likely moving soonish to a new machine gun that will replace both the 240 and the M2 BMG in the infantry battalions with something in the .338 range they are likely seeking to get back some of their investment costs on the civilian market... At least that would be my guess. If they thought they were about to get a .gov contract for their product then they would not be committing to selling anything on the open market....
"So strong is this propensity of mankind, to fall into mutual animosities, that where no substantial occasion presents itself, the most frivolous and fanciful distinctions have been sufficient to kindle their unfriendly passions, and excite their most violent conflicts." - James Madison, Federalist No 10
They've been working on this for quite awhile. I've been hearing about it for years. Some folks on the civilian side are concerned it's not reloadable, which I understand isn't a concern for everyone.
The issue that might be a problem for the military is rapid fire. Hot brass is hot because it's soaking up heat from the chamber and taking that heat with it when it leaves the gun. Polymer won't suck up nearly as much heat, and heat won't just disappear so the gun is going to run hotter. I don't know at what point the polymer will start to melt or get sticky, but hotter guns wear out faster than cooler guns. What if the weight savings go *poof* because it's offset by carrying another barrel for whatever suppressive fire weapon is in use in Future War? Outside my lane, but seems like that could be a concern.
Sorta around sometimes for some of your shitty mod needs.
>puts less stress to the barrel when firedThe composite case ammo is 30 percent lighter than metal case ammo, transfers less heat to the rifle and puts less stress to the barrel when fired. The initial price of the composite case .308 Winchester rounds is $3.50 each. Metal case equivalents cost from a dollar to $2.40 per round.
I'd be interested to learn how that works, if it's not totally BS. It's not obvious that a poly case is going to do any more than brass to contain the hoop stress or reduce the bolt thrust.
How do poly cases hold up when the chamber gets nice and hot? Thermoset resins won't melt, but they'll certainly be degraded at some point. (ETA: BBI types faster than I do this morning.)
>The initial price of the composite case .308 Winchester rounds is $3.50 each. Metal case equivalents cost from a dollar to $2.40 per round.
Mil-type FMJ 7.62 could be had two years ago for ~$0.65/rd. And could be reloaded. So they're 5x on price and you can't reload the cases. And my stash of FGMM .308, widely regarded as the best all-around factory ammo in the caliber for target use, was acquired a couple years earlier when it was $0.80-0.90/rd. I don't know how they get the volume up enough to get the price down to where this makes sense for anyone to buy into.
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Not another dime.
TV commercial .308 is being advertised but it seems not to have made it to the gunzine, gunboard, youtube reports.
Code Name: JET STREAM
Originally Posted by BehindBlueI's
M60 and M240b and M2 and M249 all fire from open bolt (IIRC, part of the design intent is to keep a hot chamber from cooking off a chambered round and to let the chamber air cool during breaks in firing). If the new gun also fires from open bolt, then the heat of the chamber isn’t going to cook the resins of these cases just like the older designs are avoiding cooking off a brass case cartridge, since they aren’t sitting in the chamber waiting to be fired. The rest of the gun can get hot, too, of course, but not anything like the chamber and barrel.
Gunners or assistants are already carrying spare barrels for the machine guns (maybe not so much for the M2). I don’t remember the number, but after X rounds/minutes of fire, when possible, they are supposed to swap barrels to let the hot one cool off. Or if they can’t change during an engagement, afterwards, or after they’ve toasted a barrel with sustained fire.
That's good news for the polymer case if it can't sit in the chamber long enough to degrade, but it still leaves the gun running hotter because you don't have the brass removing heat. You can swap barrels, but if the goal is weight savings and the barrels get hotter faster and need rotated sooner, you'll need more barrels. You'll also erode the throat faster. I suppose our logistics assumes that replacements will always be readily available?
Sorta around sometimes for some of your shitty mod needs.
I believe there was a poly case shotgun shell in the US for awhile called Activ. I saw some on the trap range years ago. I don't think they're imported anymore. Looking around it seems they're still used in S. America in the dove fields. My impression was they worked just fine in a shotgun but that's apples and oranges. Pressures are a lot lower.
In the P-F basket of deplorables.
I recall the Activ shells. They had an internal steel head and rim reinforcement.
Does the conventional brass head of a compression formed AA contribute much strength? I doubt it.
As to True Velocity it is said that the plastic case has lower thermal conductivity than brass and insulates the chamber; and has lower specific heat than brass and does not "carry away" heat.
OK, where does the retained heat go?
Into the blazing powder gas, mostly. I guess you could say it heats up the base of the bullet a bit more, but I doubt much.
So we have concerns with the hotter gas eroding the bore faster.
The other thing the extra heat will do is expand the powder gas more, driving the bullet harder. This is an asset when you are loading heavily trying to get 24" 270 WCF velocity in a 16" barrel.
Is either effect great enough to tell in ordinary use? I think you would have to wear out several barrels with each case material to tell.
Code Name: JET STREAM
I have seen a few videos (both sponsored by TV, so take with a grain of salt) but they show a guy putting his hand on the barrel/chamber area and the there is little/no heat transfer. The guy said it was because the case held a lot of the heat and prevented the transfer to the barrel.
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