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Posted: 10/24/2008 2:36:29 AM EDT
[#1]
this pic belongs to Molon IIRC...
A2/A3/A4 barrel profile are the same: heavy only in the front of FSB  |
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Posted: 10/24/2008 3:00:36 AM EDT
[#2]
Government Type Barrel Profiles, used to show the 20" profiles only
 
and here's an HBAR 
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Posted: 10/24/2008 3:33:34 AM EDT
[#3]
You guys are great !
thanks for the informations, exactly what I was looking for ! Frens: I am finding a LOT of Colt AR's, but no M4 at the moment ! |
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Posted: 10/24/2008 3:36:25 AM EDT
[#4]
thanks mate! dont stop keeping your eyes open  I've sent an email to a gunshop in Finland...lets see what they can do for me ciao! |
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Posted: 10/24/2008 4:03:04 AM EDT
[#5]
Could you import a Colt AR-15 with the original barrel swapped with a SDI m4 barrel ?
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Posted: 10/24/2008 5:51:16 AM EDT
[#6]
This change in barrel profile came post-Vietnam, when it was discovered that barrels were being bent between the FSB and flash hider. Theory was that troops were using fixed bayonets as pry bars to break the metal bands on ammo packaging of various types. In other words, soldier-proofing. Has nothing to do with accuracy. The Colt (and other) HBAR continues the heavier profile under the handguards, adding stability and dampening vibrations further. Also resists somewhat the effect of a tight sling, although you really need a DCM-style free float tube for this. |
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Posted: 10/24/2008 5:57:00 AM EDT
[#7]
Interesting.. So at first this barrel profile change had nothing to do with shooting issues !
So i guess I will use my sporter II barrel to make the M16A4 clone I had in mind, and keep one of my HBAR for the Mk12mod0 clone |
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Posted: 10/24/2008 6:11:57 AM EDT
[#8]
For a Mk12, Medium contour is what you're likely after. A WOA will handle that fine for cheap, but there are other pricier barrels that are a bit nicer.
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Posted: 10/24/2008 3:47:09 PM EDT
[#9]
What do you call a medium contour ? Don't forget I am in Switzerland, and not in the USA... barrels are scarce over here
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Posted: 10/24/2008 3:55:48 PM EDT
[#10]
ar15barrels.com/profiles.shtml |
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Posted: 10/24/2008 4:09:41 PM EDT
[#11]
This change in barrel profile came post-Vietnam, when it was discovered that barrels were being bent between the FSB and flash hider. Theory was tat troops were using fixed bayonets as pry bars to break the metal bands on ammo packaging of various types. In other words, soldier-proofing. Has nothing to do with accuracy. Not true. If a A1 bent where you say, then examine at the A2 barrel. Where do you think it would bend if you used it as a "pry bar"? IIRC it has to do with muzzle rise. |
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Posted: 10/24/2008 6:52:07 PM EDT
[#12]
Another urban legend that just won't die. Below is a quote from coldblue (Lt. Colonel David Lutz, USMC, retired) on the subject matter. 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! |
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