Discussion in 'Rifle Country' started by Nature Boy, Nov 29, 2019.
Do the cartridges fit the chambers of existing guns of the same caliber, or are new guns needed?
I don't really see polymer cased ammo supplanting brass cases in civilian applications for the foreseeable, unless via a legislative angle. It could become a lower-cost alternative, like aluminum or steel, but brass is a well-known quantity with re-usability and recycle-ability on its side. There may be advantages to some classes of target shooter, but I doubt polymer is going to take the rimfire market by storm anytime soon.
Heat seems an interesting characteristic to include in this discussion -- one of the many problems with the HK/Norma caseless selective fire project was much faster barrel heating without the ejected case removing some of the heat from the system.
Compared with metals, polymers tend to be insulators rather than conductors of heat. Someone has already stated that the use of polymer cases seems to reduce chamber temperatures. My question is: what is the thermal melting/failure point of the current generation of polymer cases? What happens if/when the barrel reaches these temperatures in machine gun applications? What is the high-temperature failure mode -- is the tendency to melt, swell, split, weaken etc.?
I would think for anything meant for higher volumes of fire like a squad automatic rife they would need to fire from an open bolt due to the temp issues.
Sierra has partnered with True Velocity for this endeavor. True Velocity has stated that the cases can’t be reloaded.
Oh I can if the accuracy claims are true.
I don’t reload for the economical benefits. I do it for the increase in accuracy. Why would I do that if I can get as good or better off the shelf?
I can achieve a consistent 1/3 MOA with my hand loads but it takes a lot of time and work to do it. I’ve never achieved a sub 10 ES
Assuming these claims are true, if they are achieving it by holding tighter tolerances and consistency in the case dimensions it might cause brass manufacturers to step up their game just to survive.
I don’t want to sound like I fear change but this is disturbing me at the moment
Wonder if I could shoot that out of my M1A and then sue them for false advertising for “Sub-Half Inch”. But they were smart. They didn’t specify. Because the 308 and 6.5 ARE Sub-Half Inch....diameter calibers.
It sounds more like a informmercial than a objective, well researched test report. Modern ammunition is very mature technology and easy to manufacture. The report brags on the “improvements”’of Polymer cases but no disadvantages. Everything has trade offs.
The biggest question I have is since polymer case walls are thicker than brass (or steel or aluminum) it reduces the space for powder. Less capacity for powder will mean using faster burning powder. As we all know faster burning powder results in different peak pressures.
The steel of the chamber and barrel "rob" heat energy out of the propulsion gas. If you reduce that, you'll have more energy left for propulsion.
With a steel case head, you can run higher pressures without case head failure or pocket expansion.
So I'm inclined to accept the claims of higher muzzle velocity.
It looks like it shares some manufacturing technology with the DAG plastic 7.62 training ammo I have. Will be interesting to see where this goes. I'm sure Sierra wouldn't chose to partner with this concept lightly and slap their good name all over something likely to go the way of Etronx.
It's just a matter of time until plastic-cased (or caseless) ammunition becomes the norm IMO. The big government-level players ordering billions of rounds of ammo have every interest in saving money on brass, and military R&D in particular is always focused on reducing soldiers' weightload. Put that much institutional money into researching a technology and chances are it's going to happen. True Velocity may not be the venture that ultimately succeeds, but they've been chipping away at this stuff since the 90s and material science in plastics has just kept improving since then.
As of today though, heat is going to be the fun thing to see with these. The first thing that comes to mind is those G36s the Germans had where the plastic barrel extensions were melting after rapid fire and throwing accuracy all to hell. If cases start melting or deforming when put into a red-hot chamber, that's going to be bad news.
There are all sorts of ways to get desired performance.
Using a metallic case head soles a number of sissues right away.
Using thin copper or brass foil to line the case interior (or plating) will obviate some of the heat issues.
One of the huge advantages polymers have is that they can be designed to meet performance goals. And, once designed, the mix stays the same through the batch, unlike metallic alloys which can vary.
Which means the QC reject rate plummets, which means far, far lower productions costs. How long will companies continue to make gilding metal cases at, oh, 0.3-0.5¢ each if they can be turned out at 0.05-0.1¢ each?
Also, polymer cases could be made in nearly any desireable color, which will fit military applications in a number of ways.
Will it change the industry? It might. That's harder to say. Probably not for short run ammo like 7.62 French short, and similar oddballs. Or in rounds needing to be really rigid, think 450 nitro express, or some of the jefferies or gibbs cartridges (whic hare also small-volume production).
Now, caseless is a different proposition. The propellant needs to be moulded in a way that it can reliably hold whatever primer is to be used, and you typically need some sort of case obturation--those two nuts have yet to be cracked. The G-11 ammo was passing the -40º to 40ºC storage requirements, but it was still using a 1.5mm case head, which had to be ejected as part of the cycling. The case head also allowed necessary indexing, to keep the primer withing reach of the firing pin. No one has quite cracked the nut of a combustible case head--at least not in small arms dimensions.
Where we may see a present change (as in within our lifetimes) is in telescoped ammo, as this presents a number of advantages in how barrels are designed, as well as how magazines work and the like. Which will only affect new arms and leave extant arms as they are. Which is better suited to the status quo, which is the sort of conservatism that most businesses follow.
Or, at least that's my 2¢
If it's still cheaper to reload then reloading will always be a thing
That is according to the claims of the article.
This will come to pass about the same time they perfect the airless tire theyve been touting for 20 years as right around the corner. Driverless cars, airless tires, meat-less meat, brass-less ammo, drone delivery, Mars vacations, cashless society and robot lovemaking. No thanks!
hey, etronx was awesome. just sayin
It sort of sounded like from that Instagram post they were rolling out a commercial line of ammo soon... did anyone else get that impression? I will probably buy some when and if it becomes available but I dont see good ol brass going anywhere anytime soon. Brass has been getting the job done for almost 2 centuries and there is a reason for it, its malleable, forgiving, reloadable, reliable, rugged, tradition, etc...
reload 6000 rounds of wildcat match ammo every year and you might think there's a lot of room for improvement in brass casings. for every step, there's something annoying id love to eliminate: trimming, turning, annealing, futzing with primer pockets, donuts, fireforming, etc. and failures that could be less frequent, like split necks, head separation, loose primer pockets...
How are you going to reform a polymer case to a wildcat case dimensions?
if i can print them, i won't have to. but i wasn't so much suggesting that polymer fixed that, as i was saying there is lots of room for improvement in brass.
All I, can say is, it may be fine for the military. If it is not reloadable, than what good will it do for the advridge citizen. I, see ammo control comming.
I'd be very concerned about users breathing the consumable case gases, especially shooting from machine guns.
Well, how nice is that for the companies making ammo?
Depends on what the binder is.
Could be an organic polymer.
A point to consider:
Insurgent enemies of the past often re-used our expended or captured munitions against our troops or our allies.
This change would greatly reduce the usefulness of this material to our enemies.
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