By the decree of the Ninth Emperor of Estusia, any individual, orginisation or party that presents a service rifle design and 100 models for testing within 3 months that satisfy, under Estusian testing, the below requirements:

No more than 800mm in length
No more than 4,000g in weight loaded
Effective to no less than 800m against point targets
Chambered in caseless ammunition
Be able to fire 1,000 round without stoppage out of the box and suffer no less than 200 stoppages after 100,000 rounds in the conditions of the sandy Estusian wastelands
Use no wood in its construction
Cost no more than NSD1,000 to manufacture full-scale

will be made eligible for an award of NSD400,000,000 and a long-term contract worth up to NSD9,000,000,000 and 6,000,000 such rifles or production rights for the equivalent quantity. Service rifles that do not meet the above requirements but are still adequate and suprerior to its competitors will be awarded the long term contract as well as a lump sum, abiet worth an amount less than would have been stated proportional to the degree of failiure of the rifle's ability to meet the stated requirements.

While not meeting your cost or loaded weight requirements, Crookfur has an assault rifle that fits your other requirements.

SX23A2 Caseless Assault rifle