One of the "problems" with the P90 is the rotator is included in the magazine. I have placed the rotator on the weapon. The magazine will be a normal box, except at the feeding end there will be two spring loaded 'retainers'. When the magazine is seated on the weapon, the weapon opens these retainers to allow rounds to move into the weapon. The magazine would slide in from the front, like that of the G11, except the rounds would be horizontal, not vertical, like the FN P90.
Either when charged or fired, the bolt would ride back and the rotator would drop another round in the chamber. When the bolt rides forward, two "mandibles" would close around the rear of the casing. When the weapon is fired, the mandibles would open up as the bolt rides to the rear again, allowing the spent casing to drop out of the weapon. While this is happening, the next round is rotating into position.
For easier magazine loading, a stripper clip should be able to directly mate with the magazine. Unlike when the magazine is seated, the stripper clip shouldn't open the round retainers.
The weapons would be between 29 and 32 inches in length. Magazine capacity would be in the range of 80 rounds. The standard 5.56mm x 45mm NATO round could not be fired from this weapon, as the casing is tapered. A new, non-tapered round will have to be developed. With 80 rounds the average soldier would be able to carry 400 read-to-fire rounds, four magazines on the front of his Load Bearing Vest and one magazine on his rifle.
An alternative to using a non-tapered round would be to use a magazine based on the "Linkless Feed" principal, similar to that used on the HK73. This should allow tapered rounds to fit in long, strait magazine, however this would be a rather bulky solution.
As the bolt recoils or the bolt is charged to the rear, the rotator would swing clockwise, aligning the round with the bolt and chamber. An arm on in the right side of the magazine well would be pulled rearward at the same time the rotator is aligning the round, moving the next round in the magazine into place. Reloading via a stripper clip would be possible without detaching the magazine.
The Magazine would feature a trap door at the rear and accessible between the butt stock and the sights. A stripper clip would be inserted, then a knob on the left side would be turned clockwise until the last round in the magazine is even with the stripper clip. The rounds on the stripper clip would be pressed forward, feeding them into the magazine. Care would have to be taken to leave no spaces in the magazine.
Newer Rifle 21 images. These are to show the weapon more to scale.