Sunday, January 30, 2011

M4 carbine

The M4 carbine is a family of firearms tracing its lineage back to earlier carbine versions of the M16, all based on the original AR-15 designed by Eugene Stoner and made by ArmaLite. It is a shorter and lighter version of the M16A2 assault rifle, with 80% parts commonality.
It is a gas-operated, air-cooled, magazine-fed, selective fire, shoulder-fired weapon with a telescoping stock. A shortened variant of the M16A2 rifle, the M4 has a 14.5 in (368 mm) barrel, allowing the individual soldier to better operate in close quarters. The M4 has selective fire options including semi-automatic and three-round burst (like the M16A2), while the M4A1 has a "full auto" option instead of three-round burst. The carbine is also capable of mounting an M203 grenade launcher, the M203A1 with a 9-inch barrel as opposed to the standard 12-inch barrel of the M203 used on the M16 series of rifle.
The M4 carbine will eventually replace the M16 rifle for most combat units in the United States Army. The winner of the Individual Carbine competition may replace the M4 carbine in U.S. Army service.


The M4 was intended to replace the .45 ACP M3 submachine guns and selected M9 pistols and M16 rifle series with most Army units (this plan was thought to be changed with the development of the XM29 OICW and the XM8 carbine; however, both projects were canceled.)
The United States Marine Corps has ordered its officers (up to the rank of lieutenant colonel) and Staff Non-commissioned officers to carry the M4 carbine instead of the M9 handgun. This is in keeping with the Marine Corps motto, "Every Marine is a rifleman." United States Navy corpsmen will also be issued M4s instead of the M9.

Improved M4

On November 13, 2008, the U.S. Army hosted an invitation-only Industry Day regarding a potential future replacement for the M4 carbine. Nineteen companies provided displays and briefings for military officials. The weapons displayed included the Barrett REC7 PDW, Bushmaster ACR, FN SCAR, Heckler & Koch HK416, Heckler & Koch XM8, LWRC M6A4,Robinson Arms XCR, SIG 556, as well as Colt's own improved version of the M4, the Colt ACC-M. The goal of the Industry Day was to provide officials with knowledge as to the current state of the art, which will assist the writing of a formal requirements document.
The possible successor to the M4 carbine in the U.S. Army is the Individual Carbine. This program is to provide a new carbine for the Army, while the USMC has decided to stay with the M4 for carbine use.

Future replacement

The carbine variant of the XM8 rifle was canceled in 2005.
On November 13, 2008, the U.S. Army hosted an invitation-only Industry Day regarding a potential future replacement for the M4 carbine. Nineteen companies provided displays and briefings for military officials. The weapons displayed included the Barrett REC7 PDW, Bushmaster ACR, FN SCAR, Heckler & Koch HK416, Heckler & Koch XM8, LWRC M6A4,Robinson Arms XCR, SIG 556, as well as Colt's own improved version of the M4, the Colt ACC-M. The goal of the Industry Day was to provide officials with knowledge as to the current state of the art, which will assist the writing of a formal requirements document.
The possible successor to the M4 carbine in the U.S. Army is the Individual Carbine. This program is to provide a new carbine for the Army, while the USMC has decided to stay with the M4 for carbine use.


The M4 and its variants fire 5.56x45mm NATO ammunition (or .223 Remington ammunition) and are gas-operated, air-cooled, magazine-fed, selective fire firearms with a multi-position telescoping stock. Original M4 models had a flat-ended telescoping stock, but newer models are now equipped with a redesigned telescoping stock that is slightly larger with curvature at the end. The M4 is similar to much earlier compact M16 versions, such as the 1960s-era XM177 family. Some of those visual designs are obvious in both weapons, however most of the similarities are not very noticeable.
As with many carbines, the M4 is handy and more convenient to carry than a full-length rifle. The price is slightly inferior ballistic performance compared to the full-size M16, with its nearly 6" (15 cm) longer barrel. This becomes most apparent at ranges of 300 yards and beyond. Statistically, however, most small-arms engagements occur within 100 yards. This means that the M4 is very much an adequate weapon for the majority of troops. The marginal sacrifice in terminal ballistics and range, in exchange for greatly improved handling characteristics, is usually thought to be a worthwhile compromise.
While the M4's maneuverability makes it a candidate for non-infantry troops (vehicle crews, clerks and staff officers), it also makes it ideal forclose quarters battle (CQB). The M4 was developed and produced for the United States government by Colt Firearms, which had an exclusive contract to produce the M4 family of weapons through 2009; however, a number of other manufacturers offer M4-like firearms. The M4, along with the M16A4, have mostly replaced the M16A2 in the Army and Marines. The U.S. Air Force, for example, plans to transition completely to the M4 for security squadrons, while other armed personnel retain the M16A2. The US Navy uses M4A1s for Special Operations and by vehicle crews.
Some features of the M4 and M4A1 compared to a full-length M16-series rifle include:
  • Compact size
  • Shortened barrel 14.5 in (368 mm)
  • Telescoping buttstock
However, there have been some criticisms of the carbine, such as lower muzzle velocities and louder report due to the shorter barrel, additional stress on parts because of the shorter gas system, and a tendency to overheat faster than the M16A2.


Like all the variants of the M16, the M4 and the M4A1 can be fitted with many accessories, such as night vision devices, suppressors, laser pointers, telescopic sights, bipods, either the M203 or M320 grenade launchers, the M26 MASS shotgun, and anything else compatible with a MIL-STD-1913 Picatinny rail.
Other common accessories include the AN/PEQ-2, Advanced Combat Optical Gunsight (ACOG), and M68 CCO. EOTech holographic weapon sights are part of the SOPMOD II package. Visible and IR (infrared) lights of various manufacturers are also commonly attached using various mounting methods. As with all versions of the M16, the M4 accepts a blank-firing attachment (BFA) for training purposes.


M4 feedramps are extended from the barrel extension into the upper receiver. This can help alleviate feeding problems which may occur as a result of the increased pressure of the shortened gas system of the M4. This problem is primarily seen in full-auto applications. While some feel they are unnecessary, their perceived or real utility to others has led to the increasing availability of this feature on civilian AR-15 products.


Except for the very first delivery order, all U.S. military-issue M4 and M4A1 carbines possess a flat-top NATO M1913-specification (Picatinny) rail on top of the receiver for attachment of optical sights and other aiming devices — Trijicon TA01 and TA31 Advanced Combat Optical Gunsights (ACOG), EOTech 550 series holographic sights, and Aimpoint M68 Close Combat Optic (M68 CCO) being the favorite choices — and a detachable rail-mounted carrying handle. Standards are the Colt Model 920 (M4) and 921 (M4A1).
Variants of the carbine built by different manufacturers are also in service with many other foreign special forces units, such as the Australian Special Air Service Regiment (SASR). While the SASR uses weapons of essentially the same pattern built by Colt for export (Colt uses different models to separate weapons for the U.S. military and those for commercial/export purposes), the British SAS uses a variant on the basic theme, the Colt Canada C8SFW.
The M4 carbine will eventually replace the M16 rifle in the United States Army.

M4 MWS (Modular Weapon System)

Colt Model 925 carbines were tested fitted with the Knight's Armament Corporation (KAC) M4 RAS under the designation M4E2, but this designation appears to have been scrapped in favor of mounting this system to existing carbines without changing the designation. The U.S. Army Field Manual specifies for the Army that adding the Rail Adapter System (RAS) turns the weapon into the M4 MWS or Modular Weapon System.


The M4A1 carbine is a fully-automatic variant of the basic M4 carbine intended for special operations use. The M4A1 has a "S-1-F" (safe/semi-automatic/fully automatic) trigger group, while the M4 has a "S-1-3" (safe/semi-automatic/3-round burst) trigger group. The M4A1 is used by almost all U.S special operation units. The M4A1 is especially favored by counter-terrorist and special forces units for close quarters combat because of the carbine's compactness and firepower. These features are also very useful in urban warfare. Although the M4 has less effective range than the longer M16, many military analysts consider engagement with a non-specialized small arm above a range of 300 meters to be unnecessary. It is effective at ranges of 150 meters or less and has a maximum effective range of about 500 to 600 meters.
In the last few years, M4A1 carbines have been refit or received straight from factory with barrels with a thicker profile under the handguard. This is for a variety of reasons such as heat dissipation, which is useful due to the complaints of high-heat production from test soldiers, which occurs during full-auto and accuracy as a byproduct of barrel weight. These heavier barrel weapons are also fitted with a heavier buffer known as the H2. Out of three sliding weights inside the buffer, the H2 possesses two tungsten weights and one steel weight, versus the standard H buffer, which uses one tungsten weight and two steel weights. These weapons, known by Colt as the Model 921HB (for Heavy Barrel), have also been designated M4A1, and as far as the government is concerned the M4A1 represents both the 921 and 921HB.


USSOCOM developed the Special Operations Peculiar Modification (SOPMOD) Block I kit for the carbines used by units under its jurisdiction. The kit features an M4A1, a Rail Interface System (RIS) handguard developed by Knight's Armament Company, a shortened quick-detachableM203 grenade launcher and leaf sight, a KAC sound suppressor, a KAC back-up rear sight, an Insight Technologies AN/PEQ-2A visiblelaser/infrared designator, along with Trijicon's ACOG and Reflex sights, and a night vision sight. This kit was designed to be configurable (modular) for various missions, and the kit is currently in service with special operations units.


A second-generation SOPMOD kit (now known as SOPMOD II) is currently under development, with many different manufacturers competing for the contract. Notable bidders include Knight's Armament Company, Atlantic Research Marketing Systems (ARMS), and Lewis Machine & Tools. Daniel Defense has won the contract for the RIS-II, the next generation of rail handguards.


An April 2002 presentation by the US Army Natick Soldier Center presented by LTC Charlie Dean and SFC Sam Newland reported on lessons learned from M4 use in Afghanistan.
  • 90% of soldiers reported confidence in the weapon.
  • 20% were dissatisfied with its need of maintenance.
  • 34% of soldiers reported that their M4's handguards rattled and became excessively hot when firing.
  • 15% reported that they had trouble zeroing the M68 reflex sight.
  • 35% added barber brushes and 24% added dental picks to their cleaning kits.
  • Soldiers reported the following malfunctions:
    • 20% reported double-feeding.
    • 15% reported feeding jams.
    • 13% reported that feeding problems were usually due to magazines.
Soldiers requested the following changes:
  • 55% requested the firearm be made lighter.
  • 20% requested a slightly larger magazine.

2007 dust test

In the fall 2007, the Army tested the M4 against three other carbines in "sandstorm conditions" at Aberdeen Proving Ground, Maryland: the Heckler & Koch XM8 rifle, Fabrique Nationale de Herstal SOF Combat Assault Rifle (SCAR) and the Heckler & Koch HK416. Ten of each type of rifle were used to fire 6,000 rounds each, for a total of 60,000 rounds per rifle type.The M4 suffered far more stoppages than its competitors: 882 stoppages, 19 requiring an armorer to fix. The XM8 had the fewest stoppages, 116 minor stoppages and 11 major ones, followed by the FN SCAR with 226 stoppages and the HK416 with 233. The Army was quick to point out that even with 863 minor stoppages—termed "class one" stoppages which require 10 seconds or less to clear and "class two" stoppages which require more than ten seconds to clear—the M4 functioned well, with over 98 percent of the 60,000 total rounds firing without a problem. The Army said it planned to improve the M4 with a new cold-hammer-forged barrel to give longer life and more reliable magazines to reduce the stoppages. Magazine failures caused 239 of the M4's 882 failures. Army officials said the new magazines could be combat-ready by spring if testing went well.

Gas Piston

Complicating the Army search for higher effectiveness in the M4 is a number of observations of M4 gas piston alternatives that suffer unintended design problems. The first is that many of the gas piston modifications for the M4 isolate the piston so that piston jams require the entire weapon be disassembled. The second is that gas piston alternatives use an off-axis operation of the piston that can introduce carrier tilt, whereby the bolt carrier fails to enter the buffer tube at a straight angle resulting in part wearing. The third is that the use of a sound suppressor results in hot gases entering the chamber, regardless of a direct-gas impingement or gas piston design choice.

Saturday, January 22, 2011

මොකක්ද මේ LED තාක්ශනය?

               ඔබ TV සහ පරිගනක Monitorය දෙස බලා කොතරම් වින්දනයක් ලබනවාද, එහෙත් ඔබ මොහොතකටවත් සිතුවාද ඔබ ඇසුරු කරන TV සහ පරිගනක Monitor තව සුලු කලක් ඇතුලත ඉතිහාස ගත වන බව? දැන් කරලියට එමින් පවතින LED තාක්ශනය මෙම නව වෙනසට හේතුවයි.

ඇත්තටම මොකක්ද මේ LED තාක්ශනය.
          මෙය තවත් අලුත් තාක්ශ්නයක් ලෙස හැදින් උවත් මෙහි තිබෙන්නේත් LCD තිරයක්ම වේ. නමුත් විශේශත්වය වන්නේ සාමාන්‍ය LCD තිරයක back-light සදහා යොදා ගන්නා fluorescent light වෙනුවට මෙහි Light Emitting Diode (LED) යොදා ගැනීමයි. එනම් LED යොදායෙන තිරය පිටුපස ආලෝකමත් කිරීමයි.
               මෙසේ තිරය පිටුපස ආලෝකමත් කිරීම ප්‍රධාන වශයෙන් ක්‍රම 2කකට සිදුවේ.
      1)   LED edge lightning (Edge lit): මෙහිදී සිදුවමන්නේ LCD තිරයේ දාරයේ LED පිහිටුවා තිරය ආලෝකමත් කිරීමයි. ඉතා slim තිර  .              වලදී මෙම තාක්ශ්නය ඹාවිතා කරයි.
        2)   LED Back-light (Array lit) : ඉතා තියුනු විඹේදන බලයක් සහිත තාත්වික දර්ශන ලබා ගත හැකි මෙම තාක්ශනයකි.

පාරම්පරික LCD තාක්ශනයට වඩා LED තාක්ශනයේ ඇති වාසි.
        1)   අති පැහැදිලි (superior) picture quality.
                         LED monitors will produce deeper blacks due to “local dimming” technology. In comparison, LCD monitors produce a lower picture quality, especially when projecting dark backgrounds. The Cold Cathode Fluorescent Lamp (CCFL), which is located behind the screen, does not actually remain cool. Instead of using all of its energy to produce light, it wastes energy in the form of heat. Further, since the CCFL current flow must be kept at a high level to preserve its lifespan, LCD screens cannot be easily dimmed. This is one of the reasons why LED TVs can operate more efficiently while providing a more precise image quality.

        2)    slim ඩිසයින්.
                          LED මොනිටර්s have an ultra-thin design because of the LED backlight technology. This design makes it easy to mount your LED TV or monitor on the wall to save space.

        3)   අවම ශක්ති අවශ‍‍යතාවය.
                           LED තාක්ශනය use less power than plasma and traditional LCD's. Switching to a LED TV will save you money on your monthly electrical bill and waste less energy on producing heat. 

        4)   පරිසර හිතකාමී බව. 
                           LED මොනිටර්s are considered to be more environmentally friendly than fluorescent tubes because LED bulbs are mercury(රසදිය) and lead(ඊයම්) free. LED TVs can also operate for longer hours (15 times longer than ordinary bulbs). The overall lifespan is much longer than your average monitor. 

:-( මේක තමයි problem 1ක...
Given that it is still relatively new and that it is a superior technology, LED TVs are a little more expensive than plasma and LCD TVs. Samsung, a leader in the TV industry, has a wide range of LED TVs that range from $1,600 – $3,200 depending on the size.