definition of Wikipedia
|6.8×43mm Remington SPC|
6.8 mm Remington SPC (left) as compared to the 5.56×45mm NATO cartridge (right)
|Place of origin||United States|
|Designer||Remington Arms, USSOCOM|
|Parent case||.30 Remington|
|Case type||Rimless, bottlenecked|
|Bullet diameter||0.277 in (7.0 mm)|
|Neck diameter||0.298 in (7.6 mm)|
|Shoulder diameter||0.402 in (10.2 mm)|
|Base diameter||0.421 in (10.7 mm)|
|Rim diameter||0.422 in (10.7 mm)|
|Rim thickness||0.049 in (1.2 mm)|
|Case length||1.676 in (42.6 mm)|
|Overall length||2.315 in (58.8 mm)|
|7.45 g (115 gr) fmj||2,575 ft/s (785 m/s)||1,694 ft·lbf (2,297 J)|
|7.78 g (120 gr) sst||2,460 ft/s (750 m/s)||1,612 ft·lbf (2,186 J)|
|7.1 g (110 gr) Sierra Pro Hunter||2,500 ft/s (760 m/s)||1,525 ft·lbf (2,068 J)|
|Test barrel length: 16 in (410 mm)|
The 6.8 mm Remington SPC (AKAs: 6.8 SPC, 6.8 SPC II & 6.8×43mm) is a rifle cartridge that was developed by Remington Arms with collaboration from individual members of the U.S. Army Marksmanship Unit, United States Special Operations Command. to possibly replace the 5.56 NATO cartridge in a Short Barreled Rifle(SBR)/Carbine.
Based upon the .30 Remington cartridge, it is midway between the 5.56×45mm NATO and 7.62×51mm NATO in bore diameter and velocity. It uses a .277 (7.036mm) diameter bullet, which is the same diameter bullet as the venerable hunting cartridge .270 Winchester uses. It is particularly adaptable to current 5.56 mm NATO firearms, the cartridge overall length being comparable.
The 6.8mm SPC cartridge was designed to address the deficiencies of the terminal performance of the 5.56x45mm NATO cartridge currently in service with the U.S. Armed Forces. The cartridge was the result of the Enhanced Rifle Cartridge program. Participating in the program were U.S. Special Operations soldiers, as well as armorers and other technicians from the United States Army Marksmanship Unit. The development of this cartridge is unusual and interesting in that it was designed by actual shooters in the armed forces, instead of by industry professionals. The goal was to create a cartridge that would bridge the gap between 5.56mm and 7.62x51mm NATO.
The program started the design by using a .30 Remington case, which was modified in length to fit into magazines that would be accommodated by the magazine wells of the M16 family of rifles and carbines that are currently in service with the U.S. Armed Forces.
In tests, it was determined that a 6.5mm projectile had the best accuracy, but a 7mm projectile had the best terminal performance. Further tests showed that a 6.8mm projectile was the best compromise between the two, providing accuracy, reliability and terminal performance up to 500 meters. The combination of the cartridge case, powder load, and projectile easily outperformed the 7.62x39mm Soviet cartridge, with the new cartridge proving to be about 200 ft/s (61 m/s) faster. The resulting cartridge was named the 6.8 Remington Special Purpose Cartridge due to the size of its projectile and the fact that it was based on the .30 Remington case.
|This article does not cite any references or sources. (July 2012)|
In general, adapting an AR-style rifle to the new cartridge only requires the replacement of the barrel, bolt and magazine of the 5.56mm-chambered rifle; but to further streamline and simplify the conversion process many parts manufacturers sell complete upper receiver assemblies chambered for 6.8SPC alongside their conversion kits focusing on the key individual parts. While a complete 6.8SPC assembly is a somewhat more expensive route, the conversion of an existing 5.56mm/.223 rifle to 6.8 SPC using a complete upper assembly takes less than a minute on an AR platform rifle without the need for specialized tools or skill. In contrast, when swapping out the individual component parts, a significant level of gunsmithing experience, special tools, and time are generally required to detach the barrel from the rifle's upper receiver and the gas system, and conversely those same needs are required for the reassembly of the upper receiver with the new 6.8SPC barrel. Also, there is the issue of having to readjust the sights if a new barrel is placed on an existing upper receiver.
|This article does not cite any references or sources. (July 2012)|
The 6.8 mm Remington SPC was designed to perform better in short barreled CQB rifles after diminished performance from the 5.56 NATO when the AR15 was changed from the rifle configuration to the current M4 carbine. The 6.8 SPC delivers 44% more energy than the 5.56 mm NATO (M4 configuration) at 100–300 metres (330–980 ft). The 6.8mm SPC is not the ballistic equal of the 7.62x51mm NATO cartridge; however, it has less recoil, is more controllable in rapid fire, and lighter, allowing operators to carry more ammunition than would otherwise be possible with the larger caliber round. The 6.8 mm generates around 1,759 ft·lbf (2,385 J) of muzzle energy with a 115-grain (7.5 g) bullet. In comparison, the 5.56x45mm round (which the 6.8 is designed to replace) generates around 1,325 ft·lbf (1,796 J) with a 62-grain (4.0 g) bullet, giving the 6.8mm a terminal ballistic advantage over the 5.56mm of 434 ft·lbf (588 J). One of the enigmatic features of this cartridge, being designed for a short barrel rifle, is that the standard rifle length is 16 inches (41 cm). You only gain about 25–35 feet per second (7.6–11 m/s) per inch of barrel length past the standard 16 inch barrel (all else being equal) to around 22–24 inches (56–61 cm) with no gain in accuracy.
In recent developments (the period 2004-2012) the performance of the 6.8 SPC has been increased by approximately 200 ft/s (61 m/s) by the work of one ammunition manufacturer Silver State Armory LLC (SSA), Wilson Combat and a few custom rifle builders using the correct chamber and barrel specifications.
|Cartridge||Muzzle velocity||200 yards drop||200 yards velocity||400 yards drop||400 yards velocity|
|5.56x45 55gr M193||3,073 ft/s (937 m/s)||2.2 inches||2,353 ft/s (717 m/s)||27.8 inches||1,743 ft/s (531 m/s)|
|5.56x45 77gr OTM||2,679 ft/s (817 m/s)||3.3 inches||2,216 ft/s (675 m/s)||32.7 inches||1,810 ft/s (550 m/s)|
|6.8x43 SPC 115gr SMK||2,650 ft/s (810 m/s)||3.5 inches||2,143 ft/s (653 m/s)||35.4 inches||1,677 ft/s (511 m/s)|
|6.8x43 SPC 110gr V-MAX||2,650 ft/s (810 m/s)||3.3 inches||2,208 ft/s (673 m/s)||31.1 inches||1,811 ft/s (552 m/s)|
|7.62x39mm||2,300 ft/s (700 m/s)||3.3 inches||1,787 ft/s (545 m/s)||53.8 inches||1,324 ft/s (404 m/s)|
|7.62x51 168gr SMK||2,600 ft/s (790 m/s)||3.4 inches||2,235 ft/s (681 m/s)||32.3 inches||1,891 ft/s (576 m/s)|
Typical trajectory information from carbines with drop and velocity calculated at sea level with a 100 yard zero.
For hunters, the 6.8 SPC cartridge is a significant improvement over the 5.56mm (.223) cartridges currently available in the AR-15 platform. The latter cartridges fall below .243 of an inch (6mm), which is what many countries and states in the USA have chosen as the smallest caliber legal to humanely take medium sized game such as (But not limited to): coyotes, wild hogs, deer, black Bear, caribou, small-medium Elk. It is gaining popularity among hog hunters. By adopting 6.8 SPC, a hunter also gains the ability to use the versatile and ergonomic AR-15 platform for hunting out to 300-400 +/- yards(274.32 - 365.76+ meters) (depending on load & chamber, out of a 16" barrel, further with longer barrel).
While there are many rumors of evaluations of the cartridge by several major Federal and local law enforcement agencies, the US Drug Enforcement Administration has allowed individual agents to purchase the M6A2 D-DEA - which uses the 6.8 mm Remington SPC - as an authorized alternative to their duty weapon. In 2010 the Jordanian state-owned arms manufacturer KADDB announced that they would be producing 6.8mm rifles and carbines for the Jordanian Army. As of 2011, 6.8mm has not gained any major significant military adoption, but it has a notable following among civilian shooters.
There are currently 4 different chambers for the 6.8 SPC which yield different results. They are: 1. The original SAAMI Specifications 2. SPC II 3. 6.8x43mm (renamed 6.8 ARP)(DMR has been replaced by 6.8x43/6.8 ARP,both are/were created by AR Performance.) 4. Noveske Mod 1 designed by Noveske Rifleworks LLC. Chamber specs 3. & 4. are proprietary. Only the rifles chambered with the newer specified chamber(6.8mm Spec II, Noveske Mod 1 and 6.8 ARP chambers) can safely use the higher pressure tactical & near max-maximum handloaded ammunition. Those rifles using the Original SAAMI specs should only be used with the standard commercial cartridge pressure (Specified by SAAMI).
The first major manufacturer to offer a 6.8 mm Remington SPC chambered version of the AR-15 was Barrett Firearms Company, offering the Barrett REC7. By 2007, most major manufacturers of AR-15 type rifles for the civilian gun market (including Olympic Arms, Bushmaster Firearms International, LMT, LWRC, DPMS Panther Arms, Rock River Arms, Stag Arms, Ruger, Bison Armory, AR15 Performance, Dedicated Technology, Yankee Hill Machine, Ambush Firearms, Wilson Combat, Daniel Defense, and Remington Arms) were offering rifles in this caliber. Dedicated AR upper receiver assemblies chambered for the round are produced by a number of smaller firms. Ruger Firearms produces a 6.8 mm for their Ruger SR-556 piston-driven AR-15 variant. The Stag Arms Hunter and Tactical models utilize the newer chambers and specified twist rates to accommodate higher pressure loadings. Microtech Small Arms Research offers their version of the Steyr AUG in 6.8. Robinson Armament Co. offers the XCR-L in 6.8, which can be easily converted between 6.8, 5.56, and 7.62x39. Bushmaster offers a 6.8 chamber and barrel along with 5.56 for the ACR also.
Remington also makes a bolt-action rifle chambered for 6.8 SPC, a 24" barrel Model 700. Ruger offers their M77 Hawkeye Compact rifle with a 16.5" barrel weighing in at 6.0 pounds. Browning offers their A-Bolt rifle in 6.8 SPC, and Thompson/Center offers barrels chambered for 6.8 SPC for the G2 Contender and Encore.
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