BCM 14.5" Midlength Upper Receiver Group

[Stickman]

Bravo Company MFG (BCM) is well known in the weapon community for their solid weapon components, and we recently had a chance to grab one of their newest 14.5" barreled upper receiver groups for review.

The 14.5" barrel is what is used on the issue Colt M4, and the M4 gas system is of the standard carbine length. Used for years, the carbine length gas system has a few areas that it looses in when compared to a midlength gas system, which pushes the gas block (or Front Sight Base) out an additional two inches. I've been accused of being a little too fascinated with technical details, so I'll touch on a few of the high points of the midlength gas system. The extra 2 inches of gas tube provide for an altered dwell time as the weapon is unlocking, which results in less wear and tear on the weapon, as well as increased relaibility. In addition, it alters the felt recoil to a bit more of a push. I'm not claiming the recoil of the 5.56 is severe by any stretch, but less is always more when you are trying to get rounds on target quick. Especially if that target is shooting at you. The midlength also pushes out the Front Sight Base out farther, and that increased sight radius allows for more accurate shooting for those times when you are using your iron sights.

Below, we will take a walk through of the BCM 14.5" Midlength Upper Receiver with permanently attached flash suppressor (FS). In this case, I'm using some of the given specs off the BCM website, and illustrating those points, as well as commenting on what strikes me as important or interesting.



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http://www.weaponevolution.com/forum...9140#post19140

[Stickman]

The 14.5" barrel comes with a permanently attached muzzle device. BCM gives you a choice of different muzzle devices, and in this case we are seeing the PWS comp. This comp does a good job of controlling muzzle rise, and even tames a bit of flash. In addition, it brings the over all length (OAL) to a legal 16" when pinned and welded. The PWS comp is timed perfectly, which is the first of many clues we have into the quality of this upper

You can also see in this image that the FSB uses the standard military front sight post (FSP).

Barrels specs are listed below.

Mil-Spec 11595E - Barrel Steel

BCM barrel steel is Mil-Spec per MIL-B-11595E. This grade (CMV) of steel is a Mil-Spec steel used in the USGI M16 family of rifles; it is stronger and will last longer than the typical barrels offered in the commercial market. The Mil-Spec grade steel gets its’ additional strength and rigidity from an increase in carbon and/or vanadium in the alloy. This will offer increased barrel life and performance through use in all types of extreme environments and temperatures.


Chrome Bore and Chamber

One of the first modifications that were made to the original M16 in the mid 1960’s was the addition of the chrome lined bore and chamber. It is now a world wide standard in the industry for a battle rifle. The chrome bore and chamber is harder than the barrel steel and on the USGI M16/M4 rifles will aid in chambering, extraction, and reliability. It increases velocity, and also resist against fouling and corrosion from extended use in the field. This gives the end user a longer barrel life with less required time in maintenance and cleaning.

[Stickman]

BCM shows an obvious weld on the underside of the PWS comp. This is done to make it painfully clear to any prying eyes that this is a legal barrel. The barrels are perkerized, with the BCM specs being listed below.

Manganese Phosphate Barrel Finish

Barrels are parkerized with the manganese phosphate finish (Mil-Spec A-A-59267). Military specifications also state that the entire barrel surface is phosphate finished to create a porous surface to absorb oil as to resist against corrosion from the elements. BCM barrels are phosphated before installation of front sights. This is a much more extensive assembly operation, but insures that the entire barrel is finished and protected . . .even under the front sight base.

[Stickman]

Inspection of the FSB shows solid taper pins, a coated sling swivel, and a properly marked "F" Front Sight Base. A check of the gas tube roll pin shows it is centered and free of mushrooming on either end.

Mil-Spec F-Marked Forged Front Sight Bases

Mil-Spec for rifles issued to the troops require taller front sight bases on all flat top AR rifles. Many commercial offerings use M16A2 height front sight bases on all of their barrels regardless of what type of upper it is installed on. As a result, owners of rifles and carbines with the flat top receiver configuration can have problems getting a proper 'zero' for elevation with Mil-Spec back up iron sights. As all of the BCM uppers are built for flat top uppers, all have the proper Mil-Spec F marked front sight base to insure the correct height for iron sight zeroing when using military iron sights. Mil-Spec taper pins secure the forged front sight base with the sling swivel secured by tubular rivets.

[Stickman]

The below shown M4 feedramps are well matched to the barrel extension. You can also see in the below picture that the weapon is test fired at the factory, a reassurance for those who obsess about QC (like me).

BCM shows a chrome lined bore as well as a NATO 5.56 chrome lined chamber.

Chrome Bore and Chamber
One of the first modifications that were made to the original M16 in the mid 1960’s was the addition of the chrome lined bore and chamber. It is now a world wide standard in the industry for a battle rifle. The chrome bore and chamber is harder than the barrel steel and on the USGI M16/M4 rifles will aid in chambering, extraction, and reliability. It increases velocity, and also resist against fouling and corrosion from extended use in the field. This gives the end user a longer barrel life with less required time in maintenance and cleaning.

5.56 NATO Chambers
The USGI 5.56 NATO chamber is the best choice for effective deployment, reliability, and compatibility, of higher chamber pressures of military ammo.

[Stickman]

Overall weight of the upper receiver is reduced by use of a government profile barrel. In this case, the Daniel Defense LITE rail is installed which prevents me from showing the full barrel profile.

Government Barrel Profiles
Duty rifles are built to be carried - day in and day out. The USGI barrel profiles (often referred to as the Government Profile) enable the operator to carry their weapon for longer periods of time and deploy them faster than the heavier commercial H-Barrel counterparts. The government profile barrel is also compatible with the current M203 mounting systems.

[Stickman]

The below link is to a writeup on Military Times featuring the BCM 14.5" Midlength above shown in this thread.


http://militarytimes.com/blogs/gears...t-flash-hider/