What to look for when buying A2 AR barrels?

[Tactically Fat]

As you know there's a metric crap ton of information out there regarding the AR platform. (And, as you also know, a metric crap ton is 1.6x a regular crap ton, but still not quite as much as a long crap ton.)

I have it in mind to build at least 1 "clone" rifle. In my mind, I'm thinking probably a 20" gun with a fixed stock. Probably not "national match" quality since I don't have a NM rear sight set. Anyhow...

I also think that I may want something like a dissipator clone or which ever model it was with the shorter proportions / super long flash hider on it. But I've heard that true dissipator guns are hard to get running right IF you make it a true clone. Apparently now there's a company that's making faux dissy barrels with carbine or mid-length gas tubes. I'm digressing again.

So - where to begin to even look at barrels? I don't need to spend a bunch of money on these things; but at the same time I don't want crap, either?

Is it more economical to buy a barrel that already has the FSB/Gas block (and maybe D-Ring) already assembled? Or potentially buy a barrel separate and then mount the FSB and other sundries to it? (provided correct diameter)? I'd think there's more to go wrong doing that, right? Like need an F2 marked FSB or somehing?

I'm rambling.

What say you all?

 

[Ark]

I did a build with a Del-Ton lightweight profile barrel that came FSB installed and barrel nut on. It was aligned properly and easy to assemble. Shot okay for a cheap barrel. I'd want better for a serious gun, though.

 

[mike4]

If you want an A2 clone AR, that is in reference to M16A2; the configuration would be a 20" A2 profile barrel on an A2 fixed carry handle upper receiver. You can find photos all over online, but the A2 profile is "heavy" in front of the front sight and reduced diameter under the hand guards. For the lower you would have an A2 fixed stock and A2 pistol grip. Notice everything on an A2 is called "A2"?! That's because all these changes were first introduced in the change from M16A1 to M16A2.

No need for NM sights, which would not be "clone correct" for a general issue M16A2. I had a particularly accurate 20" upper with A2 sights where two of us were shooting 1.1" groups at 100 yards with the iron sights.

If you want to build the same rifle with a flat top upper, you are looking at an M16A4 if you want an issue rifle clone. The front sight base looks similar between an M16A2 and M16A4 but there are minor height differences to align with the detachable carry handle, so a flat top upper receiver (M16A4) is where you want the "F" marked front sight base indicating this height difference. Other than the FSB there is no difference between an M16A2 and M16A4 barrel, both are 1 in 7" twist chrome-lined. They also share the same A2 flash hider and crush washer. Btw, chrome lining is the most important pass/fail criteria for any AR upper I build for corrosion resistance and barrel life; this was proven in military service before anyone under 50 was born.

If you research the process you can assemble an upper yourself with a proper barrel wrench, a good torque wrench, and proper grease on the barrel threads (search up US military TM's for the grease). Mounting an AR FSB is a non-trivial machining operation, not just an assembly process like most other steps in building an AR. For the traditional/USGI fixed front sight I strongly recommend buying a barrel with FSB installed.

Finally "dissipator" and "super long flash hider". These are two difference things. For the long flash hider you may be thinking of 11.5" barrels with overly long flash hiders permanently attached to reach a 16" total barrel length to keep a rifle non-NFA. Some of those may be various near clones of the XM177 series CAR rifles that saw more limited issue in Viet Nam.

The whole point of the dissipator concept is to stay as short as possible on barrel length while maintaining the full sight radius of the standard 20" barrel's FSB location. These might have been done by cutting down a standard 20" upper and enlarging the gas port, and that is indeed a good way to create an unreliable piece of crap; if it does run it will be very sensitive to the action getting dirty with normal use, and variation between ammo because there is such a short duration of pressure to operate the action after the bullet passes the gas port in the FSB and before it leaves the barrel.

Any decent dissipator type upper will have the FSB mounted in the 20" barrel position but with no gas port located there, a very short barrel length beyond the FSB with a normal A1, A2 or whatever other flash hider you want, and then the functional gas port is typically located at the CAR/M4 position on the barrel using a low profile gas block which is concealed under the full length A2 handguards.

This is an oddball configuration that has no clone resemblance to any US military standard issue AR.

If you don't have or plan to acquire multiple ARs, but want something fairly close to a US issue config, I think an M4 config has the most utility with the commercial length 16" barrel (see Colt 6920 as an example), or a commercial 14.7" barrel with the A2 flash hider pinned and welded so the total barrel length exceeds 16". Issue M4 barrel is 14.5" and if you pin and weld a flash hider it has to be one that is longer than the USGI A2 flash hider to make 16".

 

[natdscott]

As you know there's a metric crap ton of information out there regarding the AR platform. (And, as you also know, a metric crap ton is 1.6x a regular crap ton, but still not quite as much as a long crap ton.)

I have it in mind to build at least 1 "clone" rifle. In my mind, I'm thinking probably a 20" gun with a fixed stock. Probably not "national match" quality since I don't have a NM rear sight set. Anyhow...

I also think that I may want something like a dissipator clone or which ever model it was with the shorter proportions / super long flash hider on it. But I've heard that true dissipator guns are hard to get running right IF you make it a true clone. Apparently now there's a company that's making faux dissy barrels with carbine or mid-length gas tubes. I'm digressing again.

So - where to begin to even look at barrels? I don't need to spend a bunch of money on these things; but at the same time I don't want crap, either?

Is it more economical to buy a barrel that already has the FSB/Gas block (and maybe D-Ring) already assembled? Or potentially buy a barrel separate and then mount the FSB and other sundries to it? (provided correct diameter)? I'd think there's more to go wrong doing that, right? Like need an F2 marked FSB or somehing?

I'm rambling.

What say you all?

Criterion chromes are shooting pretty darn well.

"National Match" barrels can be had from White Oak (WOA) from Wilson blanks, Keystone Accuracy from Green Mountain blanks, and Compass Lake (CLE) from Douglas? that are more affordable than the KriegBartLens.

Those above will usually easily shoot 3/4, sometime 5/8, rarely 1/2. This is with 77 Match ammo, or single-fed handloads. If it's over 1 MOA with 77 Mag loads, you either have a shooter problem, or something is broken, (or the barrel has 3,000 rds on it).

For reference, the "ultra premium" tubes will usually shoot 1/2 to 5/8, sometimes a lot less. Single fed stuff can be 3/8, but almost never 1/4. Contrary to the interwebz.

Probably, the shooter who can hold 1/4 minute with an AR is a helluva lot more rare than barrels that can.

 

[knutty]

Colt

 

[cosermann]

If you want a FSB on it (which is correct for an A2 build) get the barrel with it already mounted. Installing is a bit fiddly and requires special tools. Personally, I’d go 20” with rifle gas. Standard and you can mount a bayonet.

The ”dissipator” was an oddball to get the rifle sight radius with a shorter barrel.

 

[natdscott]

Colt

At one time.