remembering the HK 4.7mm caseless round, one of the main criticisms was that it's fragile in the field.

could you make a cartridge which operates on identical principles, but surround it with a brass case?#

in other words, the bullet sits inside solid propellant, and a booster charge pushes the bullet into the barrel - exept theres a case around the solid propellant.

also, could these caseless or semi-caseless rounds work well with extreme high pressures? or would it put too much strain on the chamber and action?

It’s called cased telescoped, it’s been around for a while. Look at Textron’s entry to NGSW and the French CT40

no. CT rounds have a wall at the top that surrounds the bullet. 

my round would literally just be a brass case with no roof or neck. the propellant is solid and the bullet sits all the way at the bottom

smg762 said:

my round would literally just be a brass case with no roof or neck. the propellant is solid and the bullet sits all the way at the bottom

How the round is going to headspace? On the case mouth like a pistol cartridge?

A cursory image search suggests that the H&K caseless round had a "wall" at the front to help introduce the bullet into the barrel and avoid blow-by.

Your round sounds like it would simply fire the bullet into parts of the barrel other than the chamber more often than would be desirable.

1. No.

2. Why?

HK came up with caseless in order to eliminate extraction. They needed to eliminate extraction to increase burst rate. They wanted to increase burst rate to improve Ph.

Caseless ammunition is inextricably linked to the operating system of the G11. If you aren’t compromising the design of the firearm to meet the specific purpose of the HK designers, caseless offers no benefit. Even if it worked, which it doesn’t.

Your idea makes caseless ammunition worse for no reason.