I have a Colt 9mm barrel and I am discovering a issue with the flange around the barrel the is used to bind the barrel to the upper receiver via the barrel nut.  The issue is that the 9mm barrel has a flange that is 1/3 to at most 1/2 the thickness of a 5.56 barrel's flange.

This creates a problem because when I use a barrel nut to attach the 9mm barrel to the upper receiver the barrel nut does not clamp the barrel down to the receiver before the nut hits the upper receiver.

I know I have seen some 9mm uppers, perhaps Colt, that use a washer looking spacer that fits on the outside of this flange that would provide extra thickness to allow the barrel nut to clamp the barrel to the receiver.  Does anybody know where such a washer or what ever it be called could be purchased?

I called RRA and they informed me there was no difference between the flange on their 9mm or 223 barrels so they didn't have parts available.  I am wondering if this is another Colt "let's be different" modification to mess with my mind?  I also tried the local hardware and I didn't see anything there that helped either but next trip I will take the 9mm barrel and receiver with me to try again...

Thanks for any advise!

First time I've ever heard of this, granted, I have never had my 9mm ASA apart.

I was going to look up on my Gun Parts book if the 9mm's were different, but I can't find my book and the online doesn't have a 9mm pic.

If finding a washer that is made (standard bolt washers) doesn't work, you might have to have one made.

Who did you talk to at RRA?......Not a gunsmith but RRA does list a different NUT/Delta ring for 9mm's...Maybe this is it...sorry if this doesnt help im just thinking aloud...........UNDERDOG

The 9mm barrel extension should duplicate the 223/556 extension, other than the hole for the chamber,,, 9mm being flat on the rear, 223/556 having all the lugs and stuff for accepting the bolt.

From the rear of the ring (that sits to receiver) to the face of barrel (chamber end), it should measure approx .990", and face should be even w/flat inside upper.

The flange should be approx .135" minimum (my opinion) thicker should be fine.  OD of the flange is 1.174", so long as it fits the bore of the barrel nut and allows nut to thread onto upper.

Far fetched but maybe the nut is out of spec, too long of threaded portion, or barrel flange too thin on the barrel, or the threaded portion on the upper is too short....

My RRA 9mm upper was like my .223 uppers.  When I worked on my FFL/SOT's 9mm Colt upper, it had the washer you are talking about. His upper was purchased new as a LEO only upper from a Colt distr.

Yea, I did talk with a guy at RRA and he indicated that their barrels and upper receivers were the same.  This Colt barrel, is definately not the same.  I am in the midst of a paint project but I will try to post pics later....

Thanks again for the help & advise!

Well, there....it's solved!  Now you just have to get the part or have one made... Don't you just love COLT! [:D]

Yea, you have to love Colt to make life a challange...

Here is the pic...

[img]http://quarterbore.com/images/barrelflange.jpg[/img]

On the left is the New Colt 9mm barrel and on the right is a Colt A2 5.56 barrel.  I think the difference is pretty clear.

Yup QB, you are right...the difference is really clear.

Well, I can tell you one thing, finding a washing/shim will be difficult (at least at the normal hardware store).  That's gonna have to be thick, but wide in the middle to go over the barrel.  Maybe you should email/call Colt and find out if that little part is available and how much.  Or you can contact Gun Parts Corp and see if they have it....

I finally got a chance to call Colt Customer Service and they directed me SAW in Arizona.  The person on the phone at SAW at first wasn't familiar with this issue and said that all barrel flanges are the same but they checked and... guess what...

This is something brand new on new Colt LE 9mm barrels and SAW couldn't find a part number or more info on this but there was somebody in the shop that was familiar with this system.

Now I need to call Colt "Product Service" as SAW indicated that the barrel shouldn't have been sold without this 9mm barrel spacer.  

Oh well, I'll have to call again tomorrow and see if I can get the part from Colt or if they will make me return the whole barrel.  My concern is that this already has a GG&G flip up sight mounted and I worry that Colt will tell me GG&G lost the adapter...

We will see I guess?

Uh oh... telephone dancing.... dance w/ this call and dance with that call....

Give me the ID, OD, and width you want. I'll make you one.

Thanks for the offer Joe, but I managed to call Colt and they are sending me the washer at no cost...  pretty good deal!  

The person I talked to confirmed that this is something new with Colt 9mm barrels so for those getting Colt 9mm barrels now or in the future stick this one in your memory as you can't mount one of these barrels without the spacer.  

Another Colt change to make our lives interesting I guess?

Sorry for the delay...

Here is a photo that shows the 5.56 barrel next to the 9mm barrel with the new "COLT" flange extension or what ever the hell they call their newest way to make their parts different then anybody elses stuff...

[img]http://quarterbore.com/images/colt9mm.jpg[/img]

Here is the flange mounted on the barrel...

[img]http://quarterbore.com/images/colt9mm_02.jpg[/img]

At long last I was able to build my upper and I built her on a RRA 223 flattop upper with the 9mm dust cover and 9mm brass delector, KAC Short FF RAS, and the barrel already had the GG&G flip up front.  Now I need to get another BU Rear sight but at least I can use the carry handle off my M4A3 upper....

Hope this helps someone else...