6.8x43mm LUDC
The 6.8x43mm LUDC, also sometimes 6.8 LUDC and .277 LUDC, is a rimless bottlenecked intermediate rifle cartridge that was developed jointly by Burgundie, Urcea and Yonderre to replace the 7.62x51mm, 5.56x45mm and 7.5x42mm cartridges used by the three nations respectively in short barreled rifles (SBR) and infantry carbines. Adopted as the official cartridge of the Levantine Union Defense Council by way of its logistics and caliber-streamlining project, the 6.8x43mm LUDC has been at least partially adopted by all member states of the LUDC.
| 6.8x43mm LUDC | ||||||||||||||||||||
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 6.8x43 LUDC (left), 5.56×45mm LOTA (right) | ||||||||||||||||||||
| Type | Rifle, carbine, DMR, and LMG | |||||||||||||||||||
| Place of origin |  Burgundie Urcea Yonderre | |||||||||||||||||||
| Service history | ||||||||||||||||||||
| In service | 2018–present | |||||||||||||||||||
| Used by | LUDC Non-LUDC allies See Users | |||||||||||||||||||
| Wars | Final War of the Deluge | |||||||||||||||||||
| Production history | ||||||||||||||||||||
| Designed | late 2010s | |||||||||||||||||||
| Specifications | ||||||||||||||||||||
| Parent case | 7.62x51mm LOTA | |||||||||||||||||||
| Case type | Rimless, bottlenecked | |||||||||||||||||||
| Bullet diameter | 0.277 in (7.0 mm) | |||||||||||||||||||
| Neck diameter | 0.306 in (7.8 mm) | |||||||||||||||||||
| Shoulder diameter | 0.402 in (10.2 mm) | |||||||||||||||||||
| Base diameter | 0.422 in (10.7 mm) | |||||||||||||||||||
| Rim diameter | 0.422 in (10.7 mm) | |||||||||||||||||||
| Rim thickness | 0.049 in (1.2 mm) | |||||||||||||||||||
| Case length | 1.687 in (42.8 mm) | |||||||||||||||||||
| Overall length | 2.260 in (57.4 mm) | |||||||||||||||||||
| Case capacity | 34.8–36.9 gr H2O (2.26–2.39 cm3) | |||||||||||||||||||
| Primer type | Large Rifle | |||||||||||||||||||
| Maximum pressure (C.I.P) | 58,700 psi (405 MPa) | |||||||||||||||||||
| Maximum pressure (SAAMI) | 55,000 psi (380 MPa) | |||||||||||||||||||
| Ballistic performance | ||||||||||||||||||||
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Originally developed to streamline logistics between the three LOTA allies Burgundie, Urcea and Yonderre, the 6.8x43mm cartridge is a compromise between the 7.62x51mm LOTA cartridge used by the Burgoignesc Security Forces and the 5.56x45mm LOTA used by the Armed Forces of Urcea. The compromise between the two allows for improved lethality compared to the Urcean 5.56 cartridge, delivering 44% more energy on target, while producing less recoil than the Burgoignesc 7.62 cartridge. Another advantage of the 6.8mm cartridge compared to the 5.56mm is its much higher muzzle velocity, making it considerably more effective out of carbines and short barreled rifles. Four principal types of ammunition are made officially (full metal jacket, full metal jacket tracer, super shock tip and enhanced penetrator) as well as a number of commercial offerings.
One problem with the 6.8x43mm cartridge in Yonderian service has been its similar dimensions to the 7.5x42mm cartridges used by the Yonderian Defence Force. This allows 6.8mm ammunition to be chambered in 7.5mm rifles like the FAMAG and vice versa; while a 6.8mm bullet will be able to exit the barrel of a 7.5mm FAMAG (most likely causing damage to the rifling), a 7.5mm bullet will not be able to exit a 6.8mm barrel, since the bullet is larger in diameter than the bore. Firing a 7.5mm cartriddge in a 6.8mm gun thus causes excessive pressure to build up since the bullet has nowhere to go, which can cause the rifle to explode resulting in risk of injury or death. Whether a 7.5mm cartridge actually is able to chamber in a 6.8mm barrel depends on bullet length and shape, bullet seating depth, crimping, and the volume of powder charge. Because of this danger, the Levantine Union Defense Council changed its production to longer projectiles in 2022 following a number of incidents.
Users
Anglei
Bulkh- Burgundie
Chenango Confederacy - supplied by Urcea
Copake - supplied by Urcea
Fiannria
Hollona and Diorisia
Kandara - supplied by Bulkh
Lapody
New Harren - supplied by Yonderre
Nysdra Provisional Republic
Rhotia
Tapakdore - supplied by the Burgo-Darian Mercantile Port Corporation
Unnuaq Mission State - supplied by Urcea- Urcea
Yanuban - supplied by the Burgo-Darian Mercantile Port Corporation- Yonderre
Non-state users
Former users
Varshan - used captured examples during the Final War of the Deluge