BarrettM468卡宾枪

35The Small Arms Review • Vol. 10, No. 2 • November, 2006 Visit SAR on line at: www.smallarmsreview.com The Barrett Model 648 6.8mm Rem SPC by Christopher R. Bartocci Ever since the change over from the 7.62x51mm to the current 5.56x45mm there has been controversy between two fundamental schools of thought on what a military car- tridge should be. The United States military can be summed up in one word: tradition. In the 1960s, that tradition clouded the vision that a new dawn of small arms development in both concept, mechanics and ammunition had come. Still en- trenched in the “one shot, one kill” mentality, our soldiers were sent into com- bat in Vietnam with the M14 which many considered to be an inferior weapon to the AK47 assault rifle that the enemy used. The enemy were able to lay controlled large volume of automatic fire on positions which, in a meeting engagement, will win you a fight. Our soldiers were equipped with a heavy recoil rifle that was impossible to control on fully-automatic. The accuracy was of no use because the enemy could not be seen. With much trepidation, the military adopted the AR-15 rifle destined to become the M16/M16A1. A new age of small caliber high velocity cartridges gave way to provid- ing an individual soldier with firepower he had never had before. The 5.56x45mm cartridge utilizing a .224 diameter 55-grain full metal jacketed bullet proved Left: The Barrett M648 upper receiver conversion and magazine on a Colt M4A1 lower receiver. Notice the Aimpoint M68 reflex sight and the retracted buttstock. Also notice the A.R.M.S., Inc. vertical pistol grip. Below: The M855 Ball projectile (top) and a cut-away (bottom). No- tice that there are three components to this bullet. The copper jacket, the steel penetrator core and the lead plug. This bullet design has caused the major accuracy and terminal performance problems that have been experienced with the M16A2 and M4 carbines. (Photo by Jim Wesley) 36 The Small Arms Review • Vol. 10, No. 2 • November, 2006 Visit SAR on line at: www.smallarmsreview.com to be a great asset to the American fight- ing man with the ability to have a light- weight rifle that was completely control- lable on fully-automatic fire and the sol- dier could carry more than twice the com- bat load with an M16 than he could with the heavy M14 rifle. The Third Generation M16A2 and M855 Ball With the product improvements of the M16A2 the weapon system was enhanced. Due to the heavier 62-grain bullet, 1 turn in 7 inch rifling twist and new fully adjust- able rear sight, both penetration and long range accuracy were enhanced. However, the culprit of the future problems with ammunition terminal performance would come from the ammunition, the M855 Ball. The M855 Ball is a three piece bullet consisting of a copper jacket, lead plug and a steel penetrator core in the tip. This bul- let was designed for a machine gun, not a rifle. With the onset of the Global War on Terrorism, terminal deficiencies were found using M855 Ball, particularly in M4 carbines, when striking thin, malnourished, Taliban and Iraqi soldiers. There was a serious inconsistency in at what point the bullet would yaw and splinter. Some lots of ammunition would penetrate only slightly within inches and yaw and splinter. Others would go straight through and never yaw nor splin- ter. This caused se- rous knockdown problems particularly with the decreased velocity of 14.5 inch carbine barrel. A solution put forth by the United States Special Operations Command (SOCOM) was the creation of a new and improved 5.56x45mm cartridge that would increase long range accuracy and terminal perfor- mance with consistency. Accuracy is seri- ously degraded in the M16A2/A4/M4 due to the inherent characteristics of the M855 bullet. The penetrator core degrades ac- curacy and if not manufactured properly, the center of gravity will be off causing the bullet to become a “flyer.” Addition- ally, in the area of terminal performance, there was no consistency from lot to lot on what exactly it would do upon hitting a hu- man target. The answer was the Mk 262 MOD 1 car- tridge that SOCOM adopted. This is a Si- erra 77-grain open tip match bullet loaded by Black Hills. This is undoubtedly the most effective 5.56x45mm military car- tridge in the world manufactured to match grade specifications with combat reliabil- ity. The long range accuracy was drasti- cally increased and its terminal perfor- mance enhanced. This new projectile works well regardless of the type of target and performs considerably better on hu- man targets in all known distances and conditions. This round is used almost ex- clusively by SOCOM operators in their M4A1 carbines and Mk12 rifles. This so- lution satisfied most of the SOCOM op- Right: Three bullets. The first (left) is the M855 ball projec- tile with the penetrator core shown above. The middle pro- jectile is the 77-grain Open Tip Match bullet that is loaded in the Mk262 MOD1 ammunition and the last is the 115-grain Sierra Open Tip Match bullet as loaded in the pre-produc- tion 6.8mm Rem SPC cartridge. Left: Performance chart compar- ing the terminal performance of the 5.56 M855 Ball, 5.56x45mm Mk262, MOD 0 and two 6.8mm SPC cartridges. Notice the simi- larity of the Mk262, MOD 0 and the 110-grain 6.8mm SPC car- tridge. The penetration and tem- porary/permanent wound cavities are very comparable. The other two show significantly more pen- etration. Courtesy USSOCOM 37The Small Arms Review • Vol. 10, No. 2 • November, 2006 Visit SAR on line at: www.smallarmsreview.com erators: except for one. The 6.8x43mm REM SPC The 5th Special Forces, particularly MSG Steve Holland, felt that there was still room for improvement. The concept was not original. The U.S. military experimented with the possibility of the 6mm caliber pro- jectile being the ideal compromise of accu- racy, range and terminal performance. In the late 1970s the concept was abandoned in favor of the 5.56x45mm battle rifle. With the assistance of the U.S. Army Marksmanship Unit, Holland came up with a concept for a 6mm cartridge that could be fired in the M4 platform. The starting point was the .30 Remington cartridge which is merely a rimless .30-30 Win. round. It was trimmed and resized to accept a 6.8mm pro- jectile. This concept, along with the hand- loaded experimental ammunition and CAD drawings went to Remington Arms. Rem- ington wanted to aid in the Global War on Terrorism so they took on the task of devel- oping the ammunition. The 6.8mm REM SPC cartridge has been mostly a myth for the last few years due to the fact it has been developed quietly and kept proprietary. No ammunition has been made as of this writing in large quantities due to the fact the ammunition is being per- fected before it will be shipped. Reming- ton has reported three small runs of ammu- nition including ball and match grade am- munition. Hornady has also produced some loads in this new caliber. The Firearms Prototype rifles were manufactured by Precision Reflex, Inc. (PRI). Dave Dunlap assembled upper receivers with free float- ing handguards or A.R.M.S., Inc. SIR sys- tems and the OPSINC silencer and muzzle break. Dunlap also was charged with de- signing the magazine which is different from the standard 5.56x45mm magazine. Cur- rently, PRI has been the only producer of 6.8x43mm Rem SPC magazines. PRI also produces complete upper receivers cham- bered in the 6.8x43mm Rem SPC cartridge. The Barrett M648 At the 2004 SHOT Show, Ronnie Barrett unveiled a new product line: his M648. This company, dedicated to .50 BMG caliber special- ized weapons, introduced the first production 6.8x43mm Rem SPC fire- arm and has taken the lead on this project. While the cartridge is still technically under development (to be more correct would be to say “tweaked”), Barrett has teamed up with Peter Forras to work with Remington to optimize the weapon and cartridge. Forras has spent much time down at Remington working with them to perfect the 6.8x43mm car- tridge. The rifle has been based on the standard M16-platform. Barrett offers the rifle in both commercial and law enforcement/ military configurations. The “bells and whistles” are the same for both versions, the only real difference is the use of selec- tive fire, flash suppressors, bayonet lugs and telescopic stock on the law enforce- ment/military models. The weapon as offered uses a mid-length gas system developed by Mark Westrom of ArmaLite, Inc. This mid length gas sys- tem changes the location of the gas port by placing it further forward than the car- bine and slightly behind the rifle. This gives two major advantages: reliability and durability. By putting more distance be- Close-up showing the threads and thread protector for mounting a silencer. The front sight is engaged on this Barrett designed front sight assembly. This particular carbine is equipped with a muzzle break. This greatly increases controllability on full automatic. Right: To the left is a 100-grain Barnes X bullet that was fired at 50 yards into a 1/4 inch steel plate. The same bullet (right) fired into ballistic gelatin. 38 The Small Arms Review • Vol. 10, No. 2 • November, 2006 Visit SAR on line at: www.smallarmsreview.com tween the bolt carrier and gas port, lower port pressures are created resulting in the bolt assembly’s velocity being slower. This increases reliability in extraction as well as extending the life of the bolt and some of the trigger components. The barrel is manufactured by Fred Fedderson. This 1 turn in 10 inch twist barrel is chrome plated and is currently available in 16 inch length only. Barrett has plans on offering 12 and 20 inch bar- rels in the near future. The commercial version has a muzzle check similar to the one used by ArmaLite, Inc. The law en- forcement/military versions use the stan- dard M16-style muzzle break/compensa- tor The M648 gas block utilizes a folding front sight assembly. This assembly was designed by Barrett. On the law enforce- ment/military version, there is a threaded collet on the edge of the gas bock to in- stall the silencer. The Mid-Length SIR System The A.R.M.S. Inc. SIR (Selective Inte- grated Rail) system developed by Richard Swan is the solution for many problems associated with military use of this type of weapon system. The SIR system is a free- floating handguard assembly that attaches to the carrying handle by a sleeve that goes on top of the rail (thus protecting it) as well as directly to the barrel nut. This give an extended top rail that runs the entire length of the upper receiver to the front sight as- sembly. There are four Mil-Std 1913 rails that enable optics, laser, flashlights and whatever other accessories that may be needed for the rifle with no effect on the barrel and its performance. Free floating a military weapon has many benefits. First would be accuracy. With nothing impeding on the harmonics of the barrel, better uniform accuracy is achieved. Additionally, the barrel remains cooler as there is significantly better air circulation enabling the weapon to fire longer on full automatic fire. Another ben- efit, particularly with a hot barrel, pulling down on a vertical fore grip will not cause the barrel to bend or droop. The SIR sys- tem may also have a M203 grenade launcher attached to it. All the current models of the M648 feature the A.R.M.S. Inc. SIR system as well as the ARMS #40 L emergency flip-up backup sight. The Bolt The bolt carrier is standard M16/AR- 15. The difference lies in the bolt itself. The bolt was designed by Chris Barrett and is manufactured by Lewis Machine & Tool (LMT). The bolt uses the trade- mark dual extractor spring “lobster tail” extractor manufactured by LMT as it is more durable and reliable. The bolt has other similarities to the LMT Enhanced bolt but Barrett made some changes in materials and specifications specifically for the M648. The bolt has a nickel plat- ing on it. Configurations The M648 comes as a full weapon with fixed rifle stock as well as selective fire carbine lower receiver with the telescopic buttstock. The system is also sold as an upgrade or a conversion kit which will in- clude the entire upper receiver assembly and magazine. The conversions can be obtained with either selective fire bolt car- riers or semiautomatic only. It should be noted that when putting a conversion on a standard selective fire carbine lower re- ceiver, the “H” buffer should be used. This is the buffer with two steel weights and one tungsten. If the standard three steel weight buffer is used the carbine may experience bolt carrier bounce resulting in light strikes on full automatic. This is not an issue with the full length rifle se- Below: Close-up view of the A.R.M.S. SIR system that was specifically designed for the Barrett M648. Notice it says CAL 6.8 just above the end of the ejection port. This is the special design for the mid-length gas system. The bottom of the hand guard may be removed to install a grenade launcher. Left: The bolt utilized on the M648 designed by Chris Barrett. It is a modified version of the LMT En- hanced bolt but customized for the 6.8 SPC cartridge. Notice the “lob- ster tail” extractor with dual extrac- tor springs. 39The Small Arms Review • Vol. 10, No. 2 • November, 2006 Visit SAR on line at: www.smallarmsreview.com lective fire lower receiver. Semiautomatic guns can use either due to the bolt group will have sufficient time to lock before the next shot is fired. There has been some discussion about Barrett eventually coming out with a piston driven mecha- nism for this weapon system. Shooting Impressions The rifle received for testing was a law enforcement/military upper receiver with a standard semiautomatic only lower re- ceiver. The author’s own Colt M4 full automatic carbine lower was used for full automatic testing. The semi-automatic only lower receiver was equipped with an LMT two-stage match grade trigger. The optics used were the M68 Aim Point Comp II, EOTech holographic sight as well as the standard backup sights. Ap- proximately 700 rounds were fired in to- tal in both semiautomatic for accuracy as well as fully automatic for functionality. The magazine used was a PRI made 28- round steel magazine. The ammunition was manufactured by Remington. Fully-automatic tests were conducted in close quarter battle conditions. Tar- gets ranged from 5 to 25 meters. The cyclic rate was about the same as the stan- dard M4 carbine and recoil was really not that much more. There was no problem controlling the weapon. The EOTech sight made shooting easier allowing both eyes to remain open increasing speed and accuracy. By adjusting the brightness of the sight, it was useful for both close tac- tical work as well as short range sniping. Conclusions The 6.8mm Rem SPC is without a doubt an improvement over the existing 5.56x45mm for military use. But the question is, how much better? The car- tridge unfortunately has a very steep up- hill battle ahead of it once the military community gets a hold of it. The weapon itself is not an issue. The M16-based design is well proven. But in order for SOCOM in particular to adopt such a car- tridge for use will be a gigantic undertak- ing. First and foremost it has to be more than better, it will have to be drastically better and offer a large advantage. Sec- ond, and perhaps the most critical, will be logistics. The cartridge will be at best used by SOCOM operators and them alone. From a logistical standpoint, add- ing a new cartridge into inventory, in par- ticular one nobody else in the service uses, can cause serious problems. Once SOCOM operators are deployed they be- come part of the unit they are assigned and along with that goes their supply. Having non-compatible ammunition can put the operators at risk given they do not have re-supply specific to them. The Barrett M648 and 6.8x43mm Rem SPC ammunition performed flawlessly and accurately. Barrett has not been too quick to go into production due to the fact they have waited until the development of the rifle and ammunition was com- pleted insuring their customers get a fi- nal production weapon and not a semi- prototype. As of this writing, after more than three years of advertising and manu- facturing of barrels to fire this new car- tridge, the ammunition has yet to be com- pleted and put into full production. This weapon and cartridge will undoubtedly find a following in law enforcement and commercial shooters and competitors. As far as the military use of this weapons system, only time will tell.