Hey guys, I should have posted this sooner but kept getting side tracked.  The barrels we talked about Green Mountain making last month have finally been finalized and they are being produced now and are expected to be available about the end of April or early May sometime.  For everyone wondering what barrels I am talking about they are going to be made in both 14.5" and 14.7" and will be the correct lightweight pencil profile of the Colt carbines.  Government profile under the handguard .625 FSB journal and .570 out in front of the FSB.

These will be great on all your retro clones, as well as modernish builds since it has the 1-7 twist instead of the 1-12 like is offered by Brownells.  I do not own one but believe the Brownells also has the wrong profile under the handguard and is a little thicker then the standard government profile based on pictures I have seen.  These should also have the standard gray parkerizing that Green Mountain puts on all their regular barrels so should match up quite nicely and also save you the worry of getting a barrel with the suppressor relief cut that has been coming on the recent Brownells ones.

Rick at Green Mountain said he would be offering these as a group buy for us with no minimum purchase number at $125 each.  The original thread to where it was requested by another member can be found over in the industry section here - Link to Thread

And to copy and paste the profile from that thread -


I just wanted to give everyone a heads up so they could figure out future build plans and get their money saved up for the end of next month.  I am hoping to pick up a couple-few myself depending on funds.  Maybe if these turn out as nice as I think they will and sell as well as they should we can talk Rick into making this same barrel in 11.5" as well since it'd be as easy as chopping off 3" at the end and use the same profile.

In for one of these I think!

Regarding 11.5" barrels- they are thicker forward of the front sight base than the 14.5" and longer barrel and do not have the step up at the muzzle.

Pinned front base sight?

This makes me warm and squishy. My CC however is cowering in the corner right now!

Pinned FSB would be a nice option but it didn't sound like that would be an option based on what I read in the original thread.

At $125 there won't be a FSB for sure!

It'd be a real nice option to have depending on how much extra.

Regular retail on these are going to be $170 I think they said.

I'll have to get at least one at $125.

Would these have rifle or M4 ramps?  I'd have to be in for one so I can justify buying another receiver to put it on.  Thanks to whomever did all the work to put this together.

Do these barrels have some sort of thread "relief" for those of us who might mount suppressors to the barrels? (I think some people call it an "undercut"?)

If only they were the correct 1/12 barrel twist!!!

^^^YEP!!!^^^

There are literally no downside to 1/7 v 1/12. There is no such thing as "over stabilized" and the amount of energy that is used to impart the spin is negligible. And barrel twist is the one "clone" feature that is never visible

That's what I'm thinking as well.

I understand the retro/clone portion but the 1/7" twist would be far more desirable to me over a 1/12 twist.

What carbines could this be used for?

I think it would be about perfect for a 651, 653, or 723, clone.

If it has M4 feedramps id be in for a 14.5

All I ever fire out of my AR rifles and carbines is M193 style, 55 grain lead core ammo, for which a 1x12” twist is optimal. Even from a non-collector, functional viewpoint, I would gain absolutely nothing from a 1x7” twist barrel, except for a decrease in both accuracy and barrel life. The 1x7” twist was adopted for the M16A2, due to the requirement for that rifle to accurately fire the extreeeemely loooong (and therefore hard to stabilize) M856 Tracer Round. I have no interest in obtaining nor in firing any of that tracer ammo for target groups.

If you really like to blast away with M855 “just becuz”, then you would be better served by a barrel with a 1x9” twist, rather than 1x7”. I know, 1x9”; the horror of it all. The 1x7” twist isn’t useful until you get into the 77 grain and heavier projectiles, which again, are not what I’m into shooting in an AR.

Nope. [from the drawing]

SSeric02 - Good to know, I thought the 11.5 lightweights were the same profile.  Were they all thicker with no step up or just certain ones?  Any idea what profile they were past the FSB?  While I would love a correct profile 11.5" I am a big fan of lightweight barrels so hope it isn't too much thicker since I'd use them on modern builds as well.

MRW - All GM barrels other then their nitrated ones are chrome lined to my knowledge, and no option for a FSB install right now.  I think they only offer one barrel right now that has the FSB installed which really is a shame since they'd probably steal most of Brownells business if they just had someone install a FSB on theirs since they are a better barrel (in my opinion).

Oldguy14- These should have M4 feed ramps but am not sure if Rick confirmed that in the end design or not but is something I want to double check myself.  Half of these barrels I plan to buy will be used for retro rifles and the other half will be going on modern builds which would need the M4 feed ramps in order to work with the new flat top receivers.  I know a rifle feed ramp is what some will prefer but these aren't retro only barrels so the M4 feedramp makes it a viable option for those who prefer to use this on a modern build as well - I figure they will sell way more of them for modern builds then retro builds anyways.

A couple notes to random replies - Green Mountain has a 30% off sale at least once or twice a year and for those who aren't in a hurry you can save a lot of money by stocking up on your barrels you plan to build with for the year during this time.  It essentially makes almost all of their AR barrels $115-125ish during this sale assuming it is 30% again this year (has been the past couple years anyways).  I think it is both during Black Friday and during Christmas.

On the twist it probably wouldn't be that hard to get him to produce them with a 1/12 twist as well if they show enough interest and these sell well enough.  While I like 1/12 twist and don't mind it on my retro builds I like having the option of being able to shoot any ammo I want so it's nice to have a 1/7 or even 1/9 twist for a barrel you may use for defense.  If I was building these rifles to be wall pieces only I wouldn't mind if they all had a 1/12 twist, I even have 1/14 twist barrels from Green Mountain.  And there really isn't any noticeable accuracy loss on going from a 1/12 to a 1/7 barrel, and I doubt the barrel life is shortened all that much but that is something I don't know much about.  A regular chrome lined barrel usually has a life of about 10-15k rounds before it really starts to drop off in accuracy so it isn't high on my concern list, if I shoot one that much I can afford a barrel swap.

1/12 has the ADVANTAGE of being correct for a 100% accurate retro, and 1/7 has the LIABILITY of being INCORRECT for a 100% accurate retro.

Your group might have been even better using a 1/12 barrel with those same bullets

Thanks Wolverine and Green Mountain for pushing this project forward!!

As for me, my retro repro carbines WILL be 100% happy since they're only reproductions anyway, using reproduction parts.  With that said, I'm far from a purist.  Most of the parts I use are reproductions anyway

If you're not happy with the 1/7" twist, than simply buy Brownell's 1/12 twist rate barrels.  I know its human nature, but you can never make 100% of the people happy, so throwing another barrel option out there hurts nothing.

Btw, I consider my AR carbines with C7 and A2 uppers to be retro now.

I'm hoping to buy 2 to 3 of these barrels.

@Wolverine08

Yes, thank you for spearheading this project.  I'm in for at least one barrel, maybe two.  Not particular about 14.5" or 14.7"  I can make either work for what I have in mind.  Chrome lined chambers and bores are  a must though, and an M4 barrel extension would be preferred.

Here's a good pic of an early RO723 barrel, very similar in profile to a RO653 barrel, especially under the hand guards.


Regarding the 11.5" Commando barrels, I measured my RO733 barrel (genuine factory Colt, late 90s vintage) awhile back with a micrometer in response to another thread.  It is 0.625" at the gas block journal/front sight base, immediately steps down forward of the front sight base to 0.615" and is that diameter all the way to the muzzle threads. There is no step back up at the muzzle end.  Here's a good image of a Colt RO733 barrel that illustrates my description.

Worries about group size due to barrel twist rate.

Shoots 55 grain FMJ.

Read the thread in industry. These were requested for A2 clone, like a 723. So pretty sure 1:7 is correct

I guess I forgot that some people now consider A2's retro.  It would be nice if they offered BOTH twists.

Do you think that your accuracy testing with the 52 grain bullets and 1x12” pencil barrel was hindered by what you described as “Very Breezy” conditions? Extreme wind conditions do play havoc with accuracy testing.

I don’t think anyone will disagree with the fact that while “pencil” profile barrels are correct for “Retro” AR builds, they are not the hot item for maximum accuracy. The pencil barrels heat up quickly, often resulting in changes in POI. Also, pencil barrels are far more prone to “barrel whip” and vibration issues, which can significantly affect accuracy.

The purpose of rifling in a bore is to stabilize a bullet in flight, that’s all. If a bullet is not stabilized, accuracy will be nonexistent. If a bullet is over stabilized, any minuscule imperfections in the bullet’s construction (and there usually are some) will be greatly magnified by the excess RPM of the bullet. The over stabilized, “imperfect” bullet will develop an in-flight “shake” to a greater degree than a properly stabilized bullet, which can certainly affect accuracy.

The point here is that everything in life, and in physics, is a compromise. There is no “free lunch” when it comes to a specific rifling twist working for ALL bullet weights/designs, however there is a correct twist rate for a particular bullet weight/design range. If this were not true, we could simply spin ALL bullets as fast as possible and everything would be “hunky dory” regarding accuracy. We all know that isn’t how it works though.

SSeric02 - Thank you for posting the pics and the dimensions, but am curious why they decided to stray from their normal .570ish profile like is on most other period correct barrels.  If I had to guess I'd say they did it to save time machining since they figured it wouldn't amount to that much of a weight difference since there isn't much barrel there past the FSB and the .615 is pretty much about what the A1 barrel steps up to at the end.  If I remember right it was anywhere from .600-.610ish on the step up.  I never noticed it being like that before but think I prefer the look of the lighter profile with step up, but it sucks it wouldn't be correct.

M16Indiana - I don't blame you for wanting a 1/12 I like 1/12 myself as well since most all I shoot is 55's but I don't see the disadvantage in the 1/7 either for a gun that could be used for multiple purposes instead of just a collectors wall piece.  I figure someone that is that concerned on it being correct would just buy an original Colt barrel anyways, or one of the ones Brownells has been offering for awhile now.  These were originally an idea by another member here posted over in the GM industry section and his idea was to copy it for the 80s-90s era colt barrels which would make the 1/7 correct.  I posted it here in the Retro section because it is where I like to frequent the most and it also gets a lot more traffic then the A2 section and is also of interest to about anyone building Retros or A2's.

Also if someone is that concerned about accuracy I doubt they are buying a sub $200 barrel to start with, 1-2 MOA is plenty good enough for anything I will ever use them for.  I have seen no accuracy loss with a 1-7 twist rate using 55 grain surplus ammo over a 1/12 twist.  But it is nice to have the option to shoot the 62's if I wish or even 69-77s for longer range if the need arises.  I haven't shot any of the 62-64grn Gold Dots/Fusions out of a 1/12 yet to see how they do but plan to here before long since that is my favorite choice for a self defense round.  I'd say they will stabilize fine for the short range but don't know if they will start to keyhole at range or not.  I still need to test that with my 1/14 twist barrel as well using the standard 55grn M193 to see if it starts to keyhole at 300+ or stays true.

A random thought not related to the Green Mountain barrels in particular.  -  With everyone getting their lowers engraved with the correct Colt/GM/FN/H&R etc. info to make them look more correct, why isn't anyone doing this with barrels?  I don't see how it would be that hard to have someone like Braceman engrave a Green Mountain barrel or Brownells Barrel to look like a factory Colt in front of the FSB as long as they mark their factory info under the handguards where it can't be seen.  It shouldn't cost that much to have done either and would be a nice touch for any retro/A2/M4 clones with aftermarket barrels.

That same profile was used on all of their 11.5" Commandos since the RO629.  You're probably right, there's no real weight savings from machining down that inch and a half, whereas on a 14.5" or 20" barrel, there is.

I'd be in for one for a 723 build.
Would a A1 birdcage pinned to 14.7" get the barrel to 16"?

I was going to ask about the same thing except would a pinned three prong pass for 16"?

Not sure the open prongs would mess up the measurement.

Thanks in advance

Yes you will be fine by pinning either an A1 or 3 prong on the 14.7" that is the reason it was the primary choice over the 14.5" since it is much harder to notice the extra .2" of barrel over an extended flash hider.  And the open prongs should make no difference,  YHM Phantoms are pinned and welded all the time and have the prongs at the end as well as many other flash hiders.

JT just pinned a 3 prong on a 14.7" for me and we have reached that magical 16" that keeps it from killing everyone.

Thank you for the great replies/info guys.

I'm excited about these barrels. I've been wanting a 1/7" pencil barrel for an A2 carbine build of mine. I love the look of a 14.7" barrel pinned and welded

I guess this carbine will have to wail just a little bit longer to get done:

Attached File

Tripping Hazard....I'm in for a 14.7 as well!

Please consider the above option, however costly and complicated it might be. Just from an overall sales point of view, I believe far more folks would be interested. The pinned/welded A2/FSB/14.7 "trifecta" should sell very, very well. Good luck.

A2?  I don't remember GM doing anything but stripped barrels (but also it doesn't mean that they haven't perhaps or wouldn't do it for enough money in play).  During one of their clearance sales I picked up a A2 profilish 16 inch and had JT put a fsb at rifle length then used a low profile gas block for my 605 (call it a tribute perhaps at least until I get the nodak 604 upper swapped but using a longer barrel isnt a true clone, at least it eliminated the need for pin welding as I am going to try my Silencerco Hybrid on it...kinda a Sionics tribute).

I'm interested.  A few items of note:
-That drawing does not show pin-holes for the FSB.  Hard to build a classic retro look with a clamp on FSB.  And depending on who you talk to, the pin holes and the FSB have to be mated together when drilled to work right (never understood that, but I know several people who jump up and down and say you can't swap pinned FSB's around).  Regardless, it'd be nice if this came with the FSB pinned on.
-how is the barrel made? (CHF, button, etc?)
-Can we get a confirmation if that's Chrome lined?
-I will say, if that's a CHF & CL - $125 is a pretty decent price.
-For my projects and interests, I have little desire to pin and weld myself.  If they could offer these in 14.7 with the option of FSB pre-installed and the A2 FH Pin and welded, I'd be a lot more interested.  
-If I had my druthers, there's no reason in 2018 to pick a 1/7 twist.  Since it's non-standard custom anyway, I'd pick 1/8.  (or maybe 1/7.7; but 1/7 will work I suppose - I won't eject over just that - but 1/7 vs vs 1/8 is a spec based more on convenience of what was picked yesterday, rather than performance benefit.  There's a reason most National Match barrels (designed for 77's and even 80's) are 1/8 and not 1/7.

Understood there will be a cost for those preferences, and I guess it just depends on how much that cost for the FSB/FH P&W adders bumps the price, for the project to still be worth my casual interest.

How do I get in on the group buy?

Some of ya'll spend way too much time READING about guns, and not nearly enough time SHOOTING them.

For a pencil barrel, non-free floated, retro rifle (which assumes open sights); if you think there will be a meaningful difference in performance between 1/7 & 1/12; you need to get your head out of the print, and spend some quality time at the range.  It also tells me, some people spend WAY too much time trying to produce itty-bitty groups from a bench, and don't really do much field shooting at all.

We did once decades ago when the wrong ammo was pulled and we had M855 for our 1/12 M16s.  Rounds keyholed and even went through sideways.  I have fired 60gr handloads and even 64gr Winchester SP in 1/12 with no problems.  The M855 projectile is longer because it is not all lead like the 64gr and destabilizes.  1/7 is really overkill for the M855 but they went that way apparently for the even longer M856 tracer.  77gr would not be a realistic option but I have fired 69gr GMM out of my 1/10 varminter......77gr shoots like a dream out of my 1/8 Douglas DCM barrel

I'm on the fence about these for a 723 build I've started. Im fairly mechanically handy but the idea of pinning the FSB myself is a little intimidating. Everyone raves about JT, what would having him do it run me or typical cost somewhere else?

Current price for JT to install fsb = $60........well worth every penny. He has done several for me.  When these barrels arrive, he will be doing another one.

How do I buy 2 of these? Are they pre-order? I did not see them on the GM site.

Thanks Jay

Thx
 Cool you were in Kodiak....the most likely candidate for my barrel is sitting in my geographically separated safe at my parents house in Homer