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Posted: 6/9/2005 1:48:43 PM EDT
[Last Edit: 6/16/2005 3:33:07 PM EDT by Krazny13]
Alright guys, I need your help.

I took my M4 in to a smith to have a DD 7.0 installed. He puts it on and when I go to shoot it I notice that the FSB is canted to the left. So much so that it is shooting about 2-3 feet right of the sights at 100 yds. I run out of windage and its still shooting to the right. How can I fix this? I cant seem to get the pins out without rounding them over, and I don't have the tools to get the barrel off.

Link Posted: 6/9/2005 2:36:29 PM EDT
[Last Edit: 6/9/2005 2:38:36 PM EDT by Dano523]
Barrel need to be correct indexed in the upper receiver socket, hence either drifted or shimmed to correct the problem is you have taper pins that are holding the FSB onto the barrel.

Do not remove the taper pins thinking that you will be able to drift the front sight base around on the barrel, the entire barrel needs to be correctly indexed on the upper receiver.

Time for you to take the weapon back to the smith to have him correct his install problem (sight plain aligned (front sight against the rear sight) with the barrel bore plain).
Link Posted: 6/9/2005 2:56:30 PM EDT
Chris, is it possible that he overtorqued the barrel nut? This could twist the barrel in the upper receiver slightly, causing you to shoot to the right.
Link Posted: 6/9/2005 5:59:05 PM EDT
I'll take it in to him on Tuesday. Hope I can get it back to sight it in soon.

I am thinking that its an incorrect indexing problem. The pins werent in all the way, so I hammered 'em in.

I think this is going to provide me with the motivation to start collecting AR armoror's tools. . .
Link Posted: 6/9/2005 9:40:14 PM EDT

Originally Posted By M4Madness:
Chris, is it possible that he overtorqued the barrel nut? This could twist the barrel in the upper receiver slightly, causing you to shoot to the right.

Nothing like the nightmares of stretched/bent barrel socket, last it checked, they don’t just bend right back with the greatest of ease.
Oh wait, I remember now, you don't need to use a torque wrench to install a barrel (must be true, I kept reading about over in the other forum).

Lets just hope that the barrel slipped in the upper socket during the install, and at worst, the barrel extension pin was bent and need to be replaced to allow the barrel/FSB to be correctly indexed.
Link Posted: 6/10/2005 9:25:41 AM EDT
Lets hope that its something simple. . . .

Otherwise I am goin to be quite pissed. . . .
Link Posted: 6/10/2005 11:05:24 PM EDT
Forgetting to grease the barrel extension flange where it contacts the nut will do this. No, its is unlikely anything is damaged BUT you need corrective action.

I hold both the upper receiver AND the barrel while torquing the nut. This requires two vises. I snug the barrel nut finger tight, then secure the barrel in the vise with shims. With heavy, full diameter barrels, very little windup is induced. Holding just the upper will always be good for 3-10 MOA of misalignment.
Link Posted: 6/11/2005 7:14:12 PM EDT
Well, I had a barrelmaker's son (Very famous barrelmaker BTW) AND a different gunsmith look at it tonight. They both think that the barrel is on straight, but the pins are in wrong which is causing the cant, (meaning a very small chance that the barrel is off) But its hard to tell. So, I am goin to have to wait until Tuesday to get it fixed.
I am quite mad, as I hoped to shoot it this weekend. Oh well, Now I hope I can fix the dammed thing without buying a new barrel. . . .
Link Posted: 6/11/2005 7:42:13 PM EDT
[Last Edit: 6/11/2005 7:44:11 PM EDT by Keith_J]
You only get ONE chance with a barrel and the FSB for taper pins. Screw it up and no more taper pins. The taper pins partially penetrate the barrel. Now you could weld repair but do you want this? Not I.

There is salvation. Fill the taper pin slots in the barrel with brass rod, tapered to match. IIRC, that is 1:48 standard taper but you should measure. Dress the pins to fit the profile and trim both ends short and square. Degrease and install with epoxy.

On the FSB, drill and tap for #8-36 setscrews. Use dog or cup point, not cone point. You might need to relieve the barrel slots a bit so the setscrew bottoms on the brass pin.

Now the FSB is adjustable, each turn of the setscrew is worth 22 minutes of adjustment on standard length barrels. You have to loosen one side before you tighten the other.
Link Posted: 6/11/2005 8:40:13 PM EDT
The Upper was already assembled, (FSB pins were drilled and pinned)
It should have been an easy reassembly, but I think he just forgot to watch the FSB as he was tightening it, as he did a really good job of alinging the forend. . . .

I'll find out on tuesday. . .
Link Posted: 6/15/2005 8:41:45 PM EDT
[Last Edit: 6/16/2005 5:38:45 AM EDT by Krazny13]
Grr. . .
More bad news. . . .

I talked to him on Tuesday and he said he saw the cant and took it apart to make sure it went together correctly, but the cant was still there. I am beginning to seriously think he twisted the Barrel when he removed the old nut, which would explain the suddenly canted FSB, and the scratches on the barrel. . . .

(I am thinking the Smith had the Barrel in the vise and the reciever in the air when he removed the old barrel nut.
I'll post pics of the old nut in the am, but its safe to say he really torqued it. )

I am wondering what recourse I am goin to have if thats the case, as my CMMG M4 profile CL 1 in 7 twist barrel would be junk. I mean, am I out the barrel?
Link Posted: 6/16/2005 12:09:48 AM EDT
I'm speechless,
Where the fuck do some of you guys find these smiths Hacks?????
Link Posted: 6/16/2005 1:06:04 AM EDT
Link Posted: 6/16/2005 1:11:03 AM EDT
[Last Edit: 6/16/2005 1:11:19 AM EDT by Dano523]

Originally Posted By Tweak:
got a leather mallet?

Fixed it for you.
Link Posted: 6/16/2005 2:18:45 AM EDT
Link Posted: 6/16/2005 9:46:17 AM EDT
Where in WI are you?
Link Posted: 6/16/2005 2:24:37 PM EDT
Southern WI, near Madison.
(But I am willing to travel)

Well, I went up and talked with him today, and picked up my now disassembled rifle.
As far as I can tell, the barrel is pretty much junk. The chrome lining looks like it's cracked and starting to flake off right in front of the chamber. (which is where I suspect the barrel got torqued) I even had him clean it, and then looked at it again to be sure, but its most definatly not mirror smooth like the rest of the barrel. (Or before I had him work on it) He of course thinks I am making shit up because I appear to be 'some punk kid' who is trying to scam him out of a barrel. His explination is that the barrel extention came loose, and that I need to buy a barrel extension wrench to have him fix it. I told him I suspected that the way he had it clamped up was the cause, and he replied that 'the wrench wasn't long enough for him to create that much force'.

He did admit twice that he had the barrel in the vise and the reciever unsupported, which I had kinda figured as a result of the scratches on the barrel. I am going to take some pics right after this gets posted and I'll post those up as well.

Anyway, He said that I should have the barrelmaker look at it, to see if they 'built it right'. (They did, but I'm going to ask if they'd inspect it and make sure it wasn't like that when it left their facility.) If its his fault, he did say he'd take care of it, but it seems like I am goin to have to jump thru a lotta hoops to get it done right.

Link Posted: 6/16/2005 2:31:45 PM EDT
Isn't he the supposed "Gunsmith"Why should you buy a tool for him to use.It's his screw up to begin with.He should be buying you a new barrel.
Link Posted: 6/16/2005 3:32:01 PM EDT
[Last Edit: 6/16/2005 3:42:16 PM EDT by Krazny13]
Alright, here are the pics:

This is the old barrel nut. (This should give you an idea of how much force was involved)

This one is of the barrel. The area circled in red is one of the 4 scratches left by the vise wneh he clamped it up. Crappy pic, I know.

Again, another pic of the vise scratches. This one has 2 of the 4 shown. (Circled in red) Hard to see, but I can't get the light right to show how bad it is.

This is a pic showing how far off the barrel is now. Before, I only needed 3 clicks left to get on target. Now, I have it cranked all the way over and it still shoots to the right.

These pics really don't show just how badly FUBARED this thing looks. And I can't get a good enough pic of the inside of the barrel to show the area where the Chrome appears to be flaking off.

More pics to follow. . . .
Link Posted: 6/16/2005 3:52:22 PM EDT
Holy crap dude. New barrel time.
Link Posted: 6/16/2005 4:09:17 PM EDT
Is your rifle a factory built or a home built?

Link Posted: 6/16/2005 4:20:28 PM EDT
[Last Edit: 6/16/2005 4:21:52 PM EDT by omar]

but the pins are in wrong which is causing the cant

The thinnest part of the pin should be on the left, left as in when you are looking down the barrel as in aiming, with the thickest part on the right side/ejection port side of the weapon.

Edited to add: That guy is a clueless hack.
Link Posted: 6/16/2005 4:30:45 PM EDT
[Last Edit: 6/16/2005 4:31:23 PM EDT by sully]
Link Posted: 6/16/2005 6:33:58 PM EDT

Originally Posted By Krazny13:
This is the old barrel nut. (This should give you an idea of how much force was involved)

Son of a ...

Chris, it's pretty obvious that my original prognosis of overtightening was correct.

How did you find this "smith"? I can guarantee you that I'd be hitting him up for some cash. Anyone can look at that barrel nut and see that that isn't normal. How can he say that he doesn't think that he's the cause for the damage? Ask him if he sees anything wrong with that barrel nut.

If possible, let Sully check it out. He taught us well in the armorer's course in Lebanon, IN.
Link Posted: 6/16/2005 7:01:18 PM EDT
[Last Edit: 6/16/2005 9:22:29 PM EDT by Krazny13]
The upper was a factory assembled CMMG complete upper purchased in the last week of August of 2004. It was reliable, accurate, and a damn nice looking upper.

Since I have had it home, I have tried to assemble the FSB and pins a couple different ways by hand. The further I insert the pins, the worse the cant gets. I am not going to force it in case I make it worse.

The reciever is suprisingly ok. Other than some small chips in the anodizing, it is fine.
Heres a pic:

And another:

I'll probably take you up on that offer Sully. As I have no real experience dealing with problems like this.

And here is another pic of the markings left on the barrel by the vise.
Link Posted: 6/16/2005 9:03:51 PM EDT
Krazny, I'm going to post my thoughts in the hometown thread.
Link Posted: 6/17/2005 12:13:39 AM EDT
Link Posted: 6/17/2005 1:40:45 PM EDT
I scrubbed the bore out making sure I got all the dirt/gunk out.

That texture still apprears on the rifling in the bore, and I dont think less than 1k rds would pit/wear on the bore that much, but who knows. . . .

Even if the bore is ok, I dont think I will put that barrel back on. 99% of my shooting is with Irons, and I really dont trust a set screw FSB on my home defense gun. (My FSB on my Service rifle is set screw, and it has a habit of working loose at the most inopportune moment. . . .)
And after looking at the amount of $$ a YHM set screw gas block would run me, plus the cost of dicking around with it just doesn't seem as cost effective as selling the barrel real cheap and buying a different one.

Link Posted: 6/17/2005 2:03:18 PM EDT
[Last Edit: 6/17/2005 2:10:07 PM EDT by BBossman]
The taper pins are removed left to right (just like a casing is ejected) and reinstalled in reverse. He may have beat the shit out of your original FSB and either replaced it with another he had on hand or tried to install a new one and had no idea what he was doing.

ETA: Once the barrel extension is installed, the barrel index pin and gas port are drilled. The FSB is then installed on the barrel, drilled, reamed for taper pins, and pins are then installed. The Barrel and FSB are now married, trying to put one from another rifle on your barrel, could account for the cant.

Link Posted: 6/17/2005 2:52:00 PM EDT
[Last Edit: 6/17/2005 3:12:13 PM EDT by Krazny13]
It is my FSB assembly, as I had a rather unique post installed, and it was the only AR he had in the shop at the time. And he woulda charged me for a new FSB. . . .

I think if the bore checks out ok, I may have him buy and maybe install an Armalite Set Screw FSB. And then I may or may not sell the barrel. But it sure as hell ain't going to be on my home defense gun after this.
Link Posted: 6/17/2005 11:33:26 PM EDT
[Last Edit: 6/18/2005 8:20:22 AM EDT by Dano523]
Didn't catch it, but your saying that the barrel extension pin is not indexed with the FSB?
Was the index like this before you took it in, or is part of the aftermath?

Also, did the rifle use a standard forearm handguard that didn't require the FSB to be removed, or did the FSB need to be remove to install some sort of forearm tube system after the barrel was installed?
Link Posted: 6/18/2005 2:12:26 AM EDT
[Last Edit: 6/18/2005 2:13:39 AM EDT by j3_]

I may have him buy and maybe install an Armalite Set Screw FSB

It might cover up some of the gas port hole in the barrel with it off center that much.
Link Posted: 6/18/2005 2:45:27 AM EDT
Link Posted: 6/20/2005 12:57:20 PM EDT
Well, I talked to the guys at CMMG.
They are real good sports about all this.

They said to check the alignment pin, as it may have been overtorqued.
So, I'll try and pull it out and get a replacement.
Link Posted: 6/22/2005 11:17:23 AM EDT
Got the pin pulled out, and it was bent. But it wasn't the main culprit. The Barrel Extension needs to be realigned.

So, anyone have a barrel extension wrench I can borrow?
Link Posted: 6/22/2005 1:09:50 PM EDT
Link Posted: 6/23/2005 3:11:14 PM EDT
Its really strange. I will try and get pics up soon. 90% of the cant is fron a bent indexing pin. I am goin to replace it, and then if it is still noticibly canted, I'll realign the barrel extension.

The Barrel is fine. I think. It just needs a refinishing and it'll be good to go. But I am using this as an excuse to build a Recce Clone. So, who wants to buy a used M4 barrel?
Link Posted: 9/24/2005 4:44:15 PM EDT
Link Posted: 9/26/2005 12:14:21 PM EDT
no shit, wtf??

I don't like the fact that this kid is doing his own home gunsmithing on this barrel and parts- he's only giving the hack smith ammo to use back against the kid.

Link Posted: 10/24/2005 6:35:48 PM EDT

Originally Posted By Tweak:
this ever get fixed?

Well it seems I'm now the owner of this barrel. Kinda wish I knew about it's WHOLE history before I bough it.

Now I'm trying to figure out how to deal with this canted FSB.

I'm looking at it.... the gas hole and index pin seem to line up alright... bore and chamber seem ok.

But it's that FSB. It's majorily canted, I give about 7 - 10 degrees out wack.

Now mind you, I bought this without the knowledge of this thread.

Imagine my surprise when I search canted and come across this.

It's a CMMG 1/7 M4 Profile barrel I bought from.... Kranzy13 in July.

Yes I know it's 3 months later, but I didn't have the funds for the LaRue I wanted till about 2 weeks ago. So I get everything togethor when I notice the FSB is canted. I mean, I can't get the damn thing aligned.

So what do I do? Break down and buy a new FSB like the YHM or a solid one like the Armalite? (Which by the way doesn't cover both holes drilled for the FSB - had a spare one I tried on it...)

So any advice?

Might CMMG be able to fix this?
Link Posted: 10/24/2005 6:59:52 PM EDT
Link Posted: 10/24/2005 7:09:56 PM EDT

Originally Posted By Tweak:
you might be able to adjust for it by turning the barrel in the upper receiver but I'd give it back to CMMG you might take the lugs out of time or take the gas tube too far over to one side.

If you pull the FSB you should be able to compare the circle in the barrel finish left by the gas port in the FSB with the gas port location itself.

I tried adjusting it in the receiver, but there is still a major cant.

I guess I'll write the CMMG guys and see if they can drill a new FSB for it. As much as I've spent on this barrel, I would be near a Mid Length Sabre barrel...

The gas port isn't a problem either. I checked the location, and it the gas port was catching the very edge of the FSB port.
Link Posted: 10/24/2005 8:03:09 PM EDT
I thought that the Barrel indexing pin was the culprit.

Email is coming.
Link Posted: 10/24/2005 8:37:32 PM EDT
[Last Edit: 10/24/2005 8:37:56 PM EDT by Krazny13]

Originally Posted By JosephR:
no shit, wtf??

I don't like the fact that this kid is doing his own home gunsmithing on this barrel and parts- he's only giving the hack smith ammo to use back against the kid.

I got tired of dealing with the smith. He basically refused to have anything to do with me, and since college started back up I haven't been able to contact him.

Replacing the Indexing pin is pretty easy. Even a 'kid' like me couldn't screw it up.

I intend to make this right.

Link Posted: 10/24/2005 8:40:50 PM EDT

Originally Posted By Krazny13:

Originally Posted By JosephR:
no shit, wtf??

I don't like the fact that this kid is doing his own home gunsmithing on this barrel and parts- he's only giving the hack smith ammo to use back against the kid.

I got tired of dealing with the smith. He basically refused to have anything to do with me, and since college started back up I haven't been able to contact him.

Replacing the Indexing pin is pretty easy. Even a 'kid' like me couldn't screw it up.

I intend to make this right.

And Krazny is trying.

I've got an email in with CMMG about the barrel. Update when I get information.
Link Posted: 11/9/2005 12:05:28 PM EDT
[Last Edit: 11/9/2005 12:06:57 PM EDT by purplecheese]

I sent the barrel, upper receiver, and the LaRue to be installed by CMMG.

They did a very nice job, needed new taper pins and crush washer. Apparently, the receiver had more play in I originally thought. It looks good, FSB is lined up nicely.

Link Posted: 11/10/2005 8:28:02 PM EDT
Looking Good.

Link Posted: 12/1/2005 2:27:07 PM EDT
Link Posted: 12/1/2005 9:45:34 PM EDT
[Last Edit: 12/1/2005 9:49:21 PM EDT by Tweak]
Link Posted: 12/3/2005 10:43:02 AM EDT

Originally Posted By Tweak:
is that hanguard as purple as it looks? let us know how it shoots

No it's not purple. I have a CAV Arms Purple set for that

When I finally make it to a range I'll let you know about it.

And big thumbs up to CMMG for fixing it up right (though I think there was something more to it than they let on about....)
Link Posted: 2/26/2006 7:29:03 PM EDT
Is there any reason this is still stickied?
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