Your post reflects the old saying that Amateurs study tactics, professionals study logistics.They try to reduce weight anywhere and everywhere for the soldier, hence the, "Ounces equal pounds, pounds equal pain." saying. All of those areas and more are the focus of weight reduction by various R&D efforts. The drive to reduce the weight of ammo it one of the reason we went from 7.62 NATO to 5.56 NATO and is what has driven 3 or 4 different .gov funded attempts by the various branches to perfect the polymer ( or hybrid metalic/polymer) rifle case.
In addition to the individual soldier think about how much ammo the military uses and the cost of moving it throughout the supply chain. Reducing ammunition weight helps the soldier but it also helps the energy cost up the entire supply chain. The US military uses billions (with a b) rounds of ammunition a year in training and operations. Reducing the weight of ammunition has big effect on a massive supply change not just the weight the soldier has to hump in the field. Not to mention the cost of producing and then dealing with the brass cases that would go away if they went caseless.
mcb: I think you are grasping at straws. I have several nephews in various branches of service as well as retired already. The eldest one who ended his career as a Delta Operator carried both an M4 and an AK47 with ammo so I don't think the weight thing is as much of a problem as you portray. Completing the mission successfully was more important to him than how hard it was to take on the mission. I also have one in the Air Force who was a loadmaster on C-5's all during the Afghanistan/Iraq war. They carried so much stuff into the war zones that I don't think the weight of the casings would create a large cost that doesn't already exist due to military logic.....
mcb: I think you are grasping at straws. I have several nephews in various branches of service as well as retired already. The eldest one who ended his career as a Delta Operator carried both an M4 and an AK47 with ammo so I don't think the weight thing is as much of a problem as you portray. Completing the mission successfully was more important to him than how hard it was to take on the mission. I also have one in the Air Force who was a loadmaster on C-5's all during the Afghanistan/Iraq war. They carried so much stuff into the war zones that I don't think the weight of the casings would create a large cost that doesn't already exist due to military logic.....
From an industrial standpoint, the military's quest for a caseless round, or a cased round using an alternative material, has to do with reducing the considerable demand brass cases create for copper and zinc; both materials that are needed elsewhere for war production.
That’s not entirely an apples-to-apples comparison, since 4.73x33mm (4.92mm measured groove to groove, U.S.-style) was only a .194-caliber 50-grain bullet at 3100 ft/sec.For every round of 5.56x45 NATO you could carry two rounds of 4.73×33mm caseless ammunition (DM11) for the HK G11 had it become reality. When you take into accoun the magazine the saving was greater. The M4 adds ~1lb for a 30rd magazine. The G11 magazine weight 1.5ls but contain 90rds.
The HK G11 ammunition, had it become reality, would have been roughly half the weight of standard 5.56x45mm NATO.
So do we revive the large-bore repeater air rifle of the 1780s? It's the ultimate caseless ammo rifle.
I'm sure that they can come up with a full-auto version.
Not much of a heat or obturation problem.
Easily silenced, too.
More the mix of compromises you need.The main failing I think is how fragile it is outside the chamber.
That "little puff of gas" is around 65K psi with the current service round.
The problem is where the leak itself is. High-temperature, high-pressure gas causes erosion. It would take some serious engineering to handle everything from the little puff it is not on up to the big worn hole it will become.
At least in the short term, designing a direct-impingement design around that could work. Give the 'little puff' plenty of space to expand, and it might still need to wait for a port down the barrel to provide the volume it would need.
The problem is where the leak itself is. High-temperature, high-pressure gas causes erosion. It would take some serious engineering to handle everything from the little puff it is now on up to the big worn hole it will become.