“The M551 Sheridan and M60A2 tank 152mm main gun/launcher had combustible cased rounds in the 1970s. The main thing we had to be careful for was not to let the rounds break in half and spill the ‘powder’ inside the tank turret. Both vehicles also fired the Shillelagh missile as well as 152mm HEAT, and TPT.”
Caseless ammo would be another solution to this problem. There was a lot of excitement about it a few decades ago but never went beyond the development stage.
Caseless ammo goes back to WWII, and the Germans tried to adopt if for the 4.7 G11 back in the 1980s to 1990 period........without success.
There was an effort to develop a plastic case. I think it was called LSAT, in the early 2000s and ...it went no where.
Reality is the brass case does a lot more than hold the case and powder, it also removes a lot of heat each and every shot. Heat that has to be transferred out of the barreled action by some other means.
The case is an integral part of the “zero” of the weapon, in the nature of the bullet pull, if it varies the pressure profile does and as such it also affects the vibration of the barrel. Brass ammo last a long time, the old FA70 primers from WWII are still good, 75 years after WWII. Even Non corrosive primers, which do not have quite the life, are still usable 40~50 years after manufacture. A lot of that is due to the sealed cartridge.
Now it you go to a glued in bullet, how does that work over time. How doe this bio degradable bullet handed humidity? How does a cartridge that is hygroscopic work in magazines? or react to shock/vibration?
Finally how do handle the elastic modulus of the fiber case? Brass cases correctly heat treated/worked have a lot of “spring” back which means one the pressure is removed they shrink form the case walls and make extraction easy. None of the fiber/plastic materials have that property when subject to high pressure, they are much more likely to show plastic deformation, filling any crack or seam, making extraction very difficult.
Of course the day may come when brass/steel cases are obsolete, but we are at 150 + years of copper/brass/steel cases, and not even aluminum has managed to replace the later two forms (except in low pressure applications).