Posts: 1,143
Threads: 51
Joined: May 2012
Lighter case materials for the current military line up there was a polymer cases 556 a few years back but it had some problems all the current cases material used by the us is brass which is heavy and kinda pricey and considering the do not reuse cases there in not an advantage for them to stick with brass, I don't think polymer cases with meet the durability required if the change it would probably be to aluminum or steel I would guess aluminum between the 2 for less wear on the guns but depending on the cost the may go steel but they want to use the existing loading machines
But to answer your second question no nothing to do with the Grendel
Per a number of discussions I've seen, one of the deterrents to using polymer or aluminum as substitutes is heat.
[INDENT]Full auto fire heats the barrel and the chamber a LOT!
Polymers tend to get unhappy with the higher temperatures.
Aluminum is a better heat conductor than brass, so cook-off becomes a problem.
Both of these issues become evident when a live round is left in the chamber after a magazine or so is expended on full auto.[/INDENT]
My hiccup with that summary is that very little quantitative information is offered to support the observations. For example, how long does a cartridge made from each of the candidate materials survive in a chamber with a temperature of 250F? 350F? 450F?
How significant are the differences? etc.
Posts: 353
Threads: 25
Joined: Jan 2012
07-23-2012, 05:38 PM
(This post was last modified: 07-23-2012, 05:48 PM by Michael.)
In an earlier life, I was involved in some projects to look at alternative calibers for the military use (as opposed to 9mm, 5.56, 7.62). The biggest problem is (without getting into a lot of milspeak) getting around/working within the DOD procurement system. The second biggest hurdle is getting our NATO allies to go along with any changes. Whether we want to admit it or not, we have to play nice with others due to treaties and defense agreements with other nations. As I understand it, some of your Spec Ops folks have more leeway in this regard than the rest of the DOD. Doubt that an alternative caliber is being looked at very seriously, since we crammed the 5.56 down their throats in the late ‘60s.
Several years ago (prior to end of the Cold War) H&K did some work with caseless ammo in the G 11. Interesting stuff, but a lot of problems with the application as I would imagine there is with the polymer cases. I know nothing about polymer cased ammo, other than what is in the article, but I think JASmith hit the nail on the head...heat...
Another consideration would be durability. MilSpec ammo gets the crap beat out of it before it gets fired. Not being a material engineer, but I wonder how well the polymer ammo would hold up to that abuse.
Posts: 1,143
Threads: 51
Joined: May 2012
The polymer ammo problems I am aware of came from heat resulting the rounds getting torn in half on extraction also if the were fired in a fluted chamber the just exploded, here is a list of the thermal conductivity of metals Aluminum is quite a bit more conductive than brass
http://www.engineeringtoolbox.com/therma...d_858.html steel case is an option but I don't think steel cases would achieve the 10% reduction also upon further research aluminum is not a viable option as it was tried in the 60s apparently it's not safe over 40,000psi the had a problem with case burn through at least not in a cost effective alloy aparently the gau30mm uses aluminum cases but the gun was designed for them and the use a special aluminum alloy that is quite expensive
I have some ideas for this, but it would be cost-prohibitive unless mass-produced in a way that could reduce the per-unit pricing, and would need a full R&D program to make happen.
GAU-8 and the drum for the A-10 has 1174 round capacity, which is a significant weight on the aircraft, at over 4,000 lbs for the loaded system. If the cases were brass or steel, it would be weight-prohibitive on the hardpoint-mounted munitions, such as AGM-65's, bombs, pods, and other external stores.
Thanks Essayons -- Should be a good alternative to follow.
I thought it was interesting that they added a little complexity in the manufacturing process by incorporating the aluminum plug in the head.
They need an alloy with other materials besides metals in it, and making the stock would utilize an unconventional fusing process where the elements are forced to fuse to each other, not by smelting, but another approach. The process is proven and used in other industries.
You could have stronger, lighter cases made from an advanced hybridalloy. You could even incorporate elasticity into it with memory, but then manufacturing processes using dies would not work if you took it that far. Lightweight is doable though.
All of the above. The Chinese now control most of the copper supplies in the world. And it is foolish to leave brass on the battlefield. Too expensive.
We are looking at either a steele case or some form of plastic. Best case would be to have the option of using brass, steele or plastic. But we are at the end of the road for brass cases in the military.
And the Army is looking at some form of general purpose cartridge (GPC) to replace both the .223 and the .308 thus reducing the number of platforms in a typical squad. Currently we have the M16/M4, the SAW (M249) in 5.56mm. the Marines have added an infantry automatic rifle (IAR). Then we have the 7.62mm weapons such as the designated marksman rifle (DMR) and the medium MG. Two rounds, two mags. Lots of logistics. As the Shooting Times article pointed out, a round like the 6.5 Grendel makes sense.
We have a similar problem with the larger rounds. We have the 20mm, the 25mm and the 30mm all doing similar missions. Makes sense to merge everything to the 25mm.
