Semi-combustible shell casings

[Tartiflette Fan]

It's not aviation, but I though better suited to this forum than Jet Blast.

Can anyone tell me why the rounds from the main cannon of an MBT are ( at least on some MBT ) semi-combustible i.e, there is only a rather small end-cap to eject and dispose of, whereas similar sized artilley pieces are still using very large brass ( ? ) shell-cases which must be more expensive, heavier, an encumbrance around the firing position. Is it because the artillery rounds are likely to spend more time in poor storage conditions and need better weather protection ?

A secondary question is whether all those empty shell-casings are recovered for rec-use ? I would think they would be because of the otherwise enormous waste, but have never seen anyreference to this.

[Sloppy Link]

MBT rounds are a fixed charge, artillery rounds consist of a number of bags of cordite depending on the range and high angle, low angle and the very rare, direct. Having a shell case allows for the round to be loaded, “Charge three” for example, the detonator being the common item. IIRC, seven bags was super charge for max range but it wears out the barrel, the recoil etc.
MBT uses a bag charge that pretty much completely burns out, I think the same size bag is used for APFDS, HESH and Smoke, means the tank can take a cocktail of ammunition but a common bag.
And yes, brass is reused wherever possible, always in peacetime.

[MechEngr]

In the confines of a tank I would certainly want the smallest amount of nearly red-hot trash spilling out of the gun as possible. And I would rather have 2 more rounds because of the reduced weight of the casing than being able to make lamp bases or other decorations from the captured brass. There needs to be some soft metal to seal the breech so it doesn't erode and so the gases don't force back into the turret. Brass is "non-sparking" so it is ideal where combustible powders might accumulate.

[soarbum]

MBT rounds are a fixed charge, artillery rounds consist of a number of bags of cordite depending on the range and high angle, low angle and the very rare, direct. Having a shell case allows for the round to be loaded, “Charge three” for example, the detonator being the common item. IIRC, seven bags was super charge for max range but it wears out the barrel, the recoil etc.
MBT uses a bag charge that pretty much completely burns out, I think the same size bag is used for APFDS, HESH and Smoke, means the tank can take a cocktail of ammunition but a common bag.
And yes, brass is reused wherever possible, always in peacetime.

Excellent reply but I thought that I'd add a bit more to your mention of supercharge. Normally supercharge is not a standard cartridge. Eg in the case of the L118, the ammunition guy/gal can make up Charge 1,2,3,4,4.5 and 5 depending on what elements they include in the standard cartridge. Supercharge (Charge 6 on the L118) is different. It comes as a sealed cartridge jam packed with as much propellant that the factory can fit in the form factor and there is nothing to add or remove, it only does supercharge.

[Sloppy Link]

Excellent reply but I thought that I'd add a bit more to your mention of supercharge. Normally supercharge is not a standard cartridge. Eg in the case of the L118, the ammunition guy/gal can make up Charge 1,2,3,4,4.5 and 5 depending on what elements they include in the standard cartridge. Supercharge (Charge 6 on the L118) is different. It comes as a sealed cartridge jam packed with as much propellant that the factory can fit in the form factor and there is nothing to add or remove, it only does supercharge.
Aha! Thank you for the finer detail, my knowledge is from the periphery, I wasn’t RA or RAC.

[Fortyodd2]

......and, to add a bit more, the bag charges on UK MBTs are very different. Whilst it is possible to put a HESH bag behind a Fin or DS round it is definitely, by design, not possible to put a Fin or DS bag behind a HESH round -;were it to do so, the turret would leave the chassis in a style similar to that displayed by T72's in Ukraine. HESH bags are Calico and "floppy". Fin or DS bags are more solid and bright orange.

[Tartiflette Fan]

Thanks to all for improving my understanding.