Where to find drawings on Government profile barrels?

Leg

Leg

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Title basically says it all. I'm trying to fing blueprints/drawings/specs on Goverment profile carbine barrels.

Thanks for the help.
 
Here is what I have. Haven't verified it for accuracy.

M4_barrel_dimension.jpg


Ahab.
 
Thanks guys,

G37; That is a great sight (I actually checked it prior to my post) and he does give a lot of detail on how he makes his barrels, which I found very interesting, but unfortunenately he gives dimensions for everything but the gov't profile.

Now that I'm thinking about it, If anyone has the dimensions for an M4A1 profile then I'd appreciate it.

I'm contemplating having a custom barrel made based off of the government specs and then beefed up slightly.

It has just never made sense to me that the profile is turned down to as little as .625 under the handguards but it's .750 under the FSB and forward. If they really wanted to beef up the barrel then why not do it under the handguards where it's going to make the most difference.

People do make HBAR (I have one in 11.5") and even medium contour, but these are a little overkill and too heavy in my opinion for a short barrel.
 
Leg said:
Thanks guys,

It has just never made sense to me that the profile is turned down to as little as .625 under the handguards but it's .750 under the FSB and forward. If they really wanted to beef up the barrel then why not do it under the handguards where it's going to make the most difference.
Click to expand...

It depends on what characteristics you are trying to make a difference to. A major factor was heat dissipation. One of the orgs did a study and found that the best strategy was to increase the heat sink only in areas that allowed free air circulation. In other words, make the barrel fatter where it is not covered by handguards. This is just what they did.
 
BattleRife said:
It depends on what characteristics you are trying to make a difference to. A major factor was heat dissipation. One of the orgs did a study and found that the best strategy was to increase the heat sink only in areas that allowed free air circulation. In other words, make the barrel fatter where it is not covered by handguards. This is just what they did.
Click to expand...
Interesting theory. I'm not sure if it's 100% true but it certainly sounds plausible. Although, that wouldn't explain why the yanks have gone to a medium contour on the M4A1 and Canada on the C8SFW.

I've also heard that at the time they had already adopted the M203 and rather than reconfigure the mount for it they simply kept the profile under the handguards the same so that it could be used on M16A1 or A2 interchangeably. I don't think that this makes a whole lot of sense since changing the front mount would be relatively cheap in the long run, but it is another explanation/rumour that I've heard.
 
The SFW is NOT a medium contour and neither is the RO921HB version of the M4A1 barrel.

Keep in mind the heavy M4A1 barrel is not the M4A1 barrel -- both profiles are used on the M4A1 - the heavy is an option when ordering the M4A1's from Colt --

The Diemaco SFW is a heavy profile under the handguard - and the RO921HB is .85'ish
 
Thanks for the clarification. What exactly is a medium contour then? I simply called it that because they don't appear to be as thick as the HBAR that I own.
 
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