[JoeFromSidney]

If they're going to carry the weight of the raw material, why not just carry completed cartridges? In any case, it will be a long time before it will be possible to print a cartridge with a brass case, smokeless powder inside, and a bullet on one end.

[babygene]

You can make glass projectile in any form you want from aquas sodium silicate solution and a little bit of microwave energy. The explosive power can be created by the electrolysis of water creating an explosive mixture of hydrogen and oxygen.

Give me ten engineers and I can make it work in a week... That would be in 2014...

[JRandomFreeper]

Brass cases are as old fashioned as paper cartridges.

/johnny

[Rebel_Ace]

You could instruct the weapon to make special use ammunition on demand. Need a round optimized to penetrate body armor? Give me 10... Need a round to fragment for maximum tissue damage? Give me 5... Need an over-charged round for a long distance shot? Give me 1... And so on and so forth. So now I am carrying the weight of the raw material, but the round I chamber can always be optimized for my next shot...

[ModelBreaker]

I should have read your post before I posted.

[SampleMan]

If the future firearm is different, I suspect liquid propellant, case less, and electric ignition.

[Yorlik803]

Unless its Caseless ammo and some sort of solid gunpowder.
But it does seem a little complicated.