STEYR ACR

[StainlessSteelCynic]

All these issues were resolved with the ammunition and the firing mechanism used by the final versions of the G11 although with other caseless designs, who knows.
For example, the G11 ammo was coated in a varnish to prevent moisture damage.

Caseless ammo is still very much alive and in use with a small section of the civilian shooting crowd.
The Austrian gunmaker Voere has a caseless ammo hunting rifle, the VEC-91.

http://www.voere.com/en/historie/vec-91.html

The LSAT research programme is looking into plastic cased and caseless ammunition to help reduce the weight of gear carried by future US soldiers.

http://world.guns.ru/machine/usa/lsat-e.html

http://en.wikipedia.org/wiki/Lightweight_Small_Arms_Technologies

There were thee problems have heard about caseless ammo.
1) Turns out the ejected brass cartridge takes a lot of heat with it. Weapons without the cooling effect of an ejected metal cartridge heat faster. The chamber will heat to a much higher temp for a similar number of rounds fired.
2) Related to 1), because the chamber on a caseless weapon gets a lot hotter, there is an increased danger of "cookoff." Cookoff is when a chambered round fires off due to the heated chamber and barrel.
3) Moisture. While the rounds themselves seemed to hold up to prolonged exposure to water, moisture still apparently got inside the ammo. While the ammo still went "bang" it caused such variation in the generated chamber pressures as to cause a real concern as to whether a bullet could fail to clear the barrel. If you fire a gun with a bullet lodged inside because of a low powder charge or misfire, it is going to ruin your whole day. Just as disquieting, if your chamber pressure varies, so will velocity and ballistic, so if you tried to fire off a magazine of "wet" caseless rounds, none would hit the point of aim and could send bullets flying off rather erratically.

I don't know if all the problems were solved in either the ACR or the G11, but I've heard the Germans were still a bit leery of cookoff and certain firing restrictions were in play for the G11.

Targan. please weigh in. You may have heard something different.