AR barrel swap question

[USAF_Vet]

I'm thinking about swapping my bull barrel out for a standard M4 14.5" (with appropriate 1.5" muzzle device, pinned and welded). Are the threads on the bull barrel the same size as an M4 profile? Don't want to buy a new barrel and not have it fit in the receiver. I'm 99% sure the threads are the same size, just want to double check.

 

[matrem]

The Barrel Extensions are the same O.D.
The barrel nut threads on the upper receiver.
Yep, you're ok doing that.

 

[John3921]

The bbls aren't threaded. The upper is threaded and there is a bbl nut that holds the bbl in place. The nut is supposed to be torqued to 40 - 80 ft lbs as required to line up the bbl nut for the gas tube.

There should not be any locktite on the threads. The mil specs call for a non-graphite based grease (aeroshell 33 specifically) As I understand it, bbl nuts are steel and the upper receiver is aluminum. The presence of graphite could cause galvanic corrosion in the threads. By using a special grease like the aeroshell 33 the potential for galvanic corrosion is minimized.

 

[taliv]

Ideally match your feed ramps.
Thread size won't be a problem.
However the barrel nut depends on what handguards or quadrail you choose.
If you are going to perm attach the brake make sure you put the parts together in the right order first. Don't get it attached and then realize you can't get the handguards on or forgot the barrel nut or gas block or something

 

[DougW]

And, you will need the proper vice, fixtures to hold your upper reciever in the vice, wrench, punches and other small tools. Not hard to do, and the instructions are probably available in a video form on YouTube.

 

[CGRifleman]

http://www.spikestactical.com/new/s...7.html?zenid=d747a7bc53b7c5d811055e748624ed6f

I used one of these for two barrel installs, I would highly recommend it. Brownells has a nice hinged one too.

 

[Cemetery21]

Thanks for your service.
As mentioned above, but bears repeating:
Your new M-4 barrel will have M4 feed ramps on the barrel extension.
Depending on when your bull barrel and upper receiver were made, they may have rifle feed ramps and not M4.
The M4 ramp on the barrel should, ideally, be mated to an upper receiver with M4 ramps. In your case, if the receiver has rifle ramps, the combo with an M4 barrel will probably feed okay.
But, if the bull barrel has rifle ramps, it would probably have feeding issues if it is later installed on another receiver with M4 ramps (most receivers made today have M4 ramps).
Google M4 feed ramps to get an idea of the difference.
http://t0.gstatic.com/images?q=tbn:ANd9GcRkYaYCDZBGxKgCzGfwduZ7GWXFBQ0CBuzruKeojcjl2F4s51JtiQ

 

[USAF_Vet]

My current upper and barrel has M4 feed ramps, so I'm good there.

 

[taliv]

cool. where'd you find a bull barrel with m4 feedramps?

 

[Redlg155]

More than likely your barrel will already have the barrel nut included and in the correct position since the nut has to be behind the flash supressor and fsb. A 14.5" barrel with a pinned and soldered flash supressor just about makes this a necessity.

 

[dprice3844444]

use a good grease on the threads,not anti seize compound.it may have graphite in it