AR Sponsor
Posted: 9/3/2008 4:00:47 PM EDT
|
What is the purpose of a government-profile barrel? Naturally, it's lighter than an HBAR, but what purpose does the 'heavy' portion towards the front serve? Isn't the barrel only going to be as strong as its thinnest point, thus making it no stronger than a lightweight barrel? Thanks to anyone who can shed some light on this.. 
|
|
As others have mentioned, GIs began using the M16A1 as a pry bar, among other things, as well as bending them when landing in Airborne jumps, and the government requested a heavier barrel profile to prevent barrel bending. However, during development of the M16A2, they realized that with a heavier profile under the handguards, the standard M203 could no longer be mounted. Therefore, the barrel was reprofiled to accept the M203 mount, similarly, when Colt designed the newest generation of M16A2 carbines, and went to the .750 barrels on the RO720, they experimented with several barrel profiles to accept the M203 mount before settling on the step cut barrel of the late 723s and 727s, and eventually used on the M4 carbine. Eventually, SOCOM requested a heavier barrel for the M4A1, and the barrel was redesigned to a medium profile contour with flats for the M203 mount. In other words, the M16A2 government profile barrel is really a compromise design, in order to accommodate the M203 but have a heavier profile to prevent bending from... operator misuse. At least, that's the way I heard it,  HTH, ~Augee |
|
This is how the heavy muzzle was explained to me while I was attending Small Arms Repair School (45B) at Aberdeen Proving Grounds in 1985. While they were making all the improvements to the M16A1 to create the M16A2, they made the muzzle heavy to help reduce muzzle jump and increase accuracy. This, along with the change in rifling twist, the flash hider with the bottom slots closed off, and the new rear sights made a big difference in the accuracy of the weapon. The flash hider with the bottom slots closed off deflected the muzzle blast up which helped decrease muzzle jump as well as decrease the dust signature from the ground when fired in the prone position. At least that's the way I heard it. I've never seen or heard of anyone using thier rifle for a crowbar or prybar. It wouldn't help by just making the muzzle thick anyway. It would just cause the bend point to move behind the front sight assembly instead of in front of it. |
Now that sounds better. |
I've heard something along those lines too. Half of it must have been a "happy mistake" and the other half was intentional. |
Not true. Colonel Lutz has explained in the past that they merely thought the barrels were bent. Much later they discovered that they actually were not. The original method for checking straightness gave a false positive because of some kind of build-up or burr on the gas port.
See above.
Much more accurate, although note my comments above.
Correct.
Many of the changes made when going from the M16A1 to the A2 were made to increase suitability for competition. The stock and barrel have competitive aspects in their design. Despite that fact, however, the M16A1 with M193 is demonstrably more accurate than the M16A2 with M855. Your comments about using the M16 barrel as a prybar are correct. |
This sounds like a much better explanation. I too have read about the barrel being used as a prybar, and had raised the B.S. flag for many years. That is until I saw a combat arms SSG of all people doing this very thing. Granted it was on a heavier MRE type plastic strap and not any sort of metal band, but still...WTF? If the myth about bending is true or not, why tempt Murphy? |
I have two uppers with Colt M16A1 barrels and love them both. They are 1-in 12 twist barrels, though. IIRC, CMMG makes a 1x7 pencil barrel. Unless you are really burning through the ammo, IMO a A1 style barrel will do. |
|
If you intend on carrying it or shooting offhand, I'd have it turned down to a government profile or get a lightweight. There's nothing really wrong with the gov't profile, though regardless of the reason, the current profile has an interesting history. No reason not to have a light handy barrel. ~Augee |
|
I'd say keep the Hbar, and just buy a lightweight gov profile barrel. I kept my Colt Hbar, and just picked up a 20 inch gov profile upper - the weight difference is tremendous. In a few weeks, I'll take the Colt Hbar and my new M1sales upper out to the range for an iron sight accuracy and function comparison. Based on my initial testing ot the M1, they'll likely come out even. FWIW, my Colt is a Sporter Match HBAR 6601, that I picked up like new 6 months ago - it didn't have any wear from the charging handle latch engaging the upper until I took it to the range! The gov profile barrel saves a lot of weight though, a lot. It's subjectively lighter than my 16 inch Hbar midlength upper. I don't have a scale to confirm things though. |
|
My dream job would be to be the corporate historian for Colt. Imagine having access to all their archives and being able to delve into questions like this and find out exactly what happened and why. Wait, on second thought, screw that. I don't want to live in Connecticut. |
|
As a guy that went from a 20" H-bar to carbines and came around to a pencil barrel 20" I can tell you it isn't just weight. The light weight has lots to do with it but it really is about balance also. I am of the age and eyesight where the extra sight radius is a big plus but the balance of a light 20" just seems so right even compared to a carbine that weighs about the same (or slightly less?) It is just a fun gun to shoot I will politely disagree with whoever talked about the lighter gun being better for off hand use . For run and gun shoots yes, but for real bull eye busting paper target shooting I will drag out the 12 pound match rifle every time I want the best results! |
|
Dug up from archives archive.ar15.com/forums/topic.html?b=3&f=118&t=260598 Coldblue Since The M16A2 Product Improvement Program (1980-1983) was my program, this is the down & dirty on the barrel thickness issue. We (Marines) were replacing a lot of "bent" barrels that were determined to be "bent" because the Armorer's Bore Drop Gauge would not freely pass through some barrels during Ordnance Inspections (LTI's). So the Logisitcs people had "Barrels Bending" on their list of "M16A1" things to "Improve" right after listing "Handguards Breaking." We "experts" thought this bending was from rough handling like during bayonet drills, etc., as an absence of any mid-barrel handguard damage in these rifles made one assume the fulcrum of such bending was the bayonet lug. So we made that part of the barel thicker because we did not want the excess weight of a full length heavy barrel. In testing using the bayonet lug as a fulcrum, and applying calibrated mechanical pressure to the muzzle, the new barrel was about 9 times more resistant to bend and take a set than an M16A1 profile. So we went with this "improvement." However, soon after I started using a bore scope with a video recorder and monitor to inspect "bent" barrels. What I found was a mound of bullet jacket material at their gas ports. This build up was caused by a burr left from drilling/reaming the gas port. This was where the Armorer's Drop Gauge was geting stuck. When we removed this "mound", the barrels would all pass the Drop Gauge. We let Colt know what we had deduced, and that is one reason they kept models of "A2's" in their line-up with A1 profile barrels. However, the A2 profile was already down the road for the US Military. So about the only advantage of the A2 profile was to give the rifle a little more muzzle hang. This was noted by most all the Operational Test paticipants, especially when they fired the standing/off-hand leg of our rifle qualification course. So my advice to mlitary armorers is to never replace a bent barrel until you visually check the gas port, or at least scrub the hell out of the gas port area with a new bore brush and an electric drill. And thank God for chrome bores! |
Great info! |
It sure is, and straight from the horses mouth (sorry Sir if you read this  ).
|
Our girls are prettier than New Jersey girls.  - BG |
AR Sponsor