The "Celeste III" was the first working production model of the Chassepot mk. XII long rifle. Compared to other Ellisian rifles the most striking feature should be the revolving cylinder magazine, which holds 6 10x132mm ultra-magnum disintegrating-sabot rounds. This type of round is also very unconventional in that it starts out in a familiar shape, but as soon as the sabot jacket around it disintegrates during firing the round's soft body stretches backwards from the hard tip, thinning and elongating the round into a 8 inch long aerodynamic needle.
The weapon's internal mechanics are quite similar to the larger mk. VII rifles, however the main differences are in the proportions. For the size of the round in question, the recoil compensator and muzzle brake are disproportionately large. By enlarging this system and making a much higher propellant-to-round ratio this weapon's recoil is much greatly reduced to make semiautomatic fire practical. As an added bonus, with so much gas funneled away from the barrel the weapon's muzzle flash and report are significantly diminished, almost to the extent of a traditional suppressor.
Considering these benefits in addition to a smaller and lighter frame, the mk. XII makes for a more versatile alternative to the typical Ellisian long rifles, while still adding significantly higher accuracy and penetration values than short-barrel carbines.
Other miscellaneous details include the fact that the entire cylinder can be ejected and discarded, to be replaced by another on the fly as opposed to sliding in new cartridges one at a time. Also, the built-in iron sights use a narrow rear aperture as opposed to the normal tangent-type sights seen on other rifles of the line.
Production of the mk. XII has been regrettably slow, with only a handful of units completed. As things stand currently, the only one in circulation is the original, the Celeste III, which one Eliram Nadiel created as a replacement for the aging, cumbersome Celeste II. It is unknown if the variant will be developed elsewhere.