First off I'm a newbie,I just bought a new Bushy XM15-E2S A3, with a 20in heavy barrel. I have been here for four years reading posts,and now I'm part of the Black Rifle fan club. You guys were great help in helping me find my rifle.

Anyway looking through the mag well into the upper, I can see the gas tube canted slightly to the right. Looking at the upper where the gas tube fits into the
X shaped hole, while letting the bolt carrier slowly forword I can see the gas tube move back to center when the carrier key comes in contact with it.

I Emailed Bushmaster and they told me to take the bolt out of the carrier, put the carrier back in the upper and tip the barrel up and it should fall out, and if it doesn't they said to bend the gas tube with a flat head screw driver
to get it to center, and that if I'm not comfortable doing this to send it to them to fix it under warranty.

So I took the bolt out of the carrier and pushed it back and forth in the upper. There is a slight ammount of friction between the gas tube and the carrier, enough to make it stick when I point the barrel up.

What do I do to fix this,or should I do anything? I havn't shot it yet so I don't know if it will cause a problem. Bending the gas tube does not sound right, why bend something that's supposed to be straight. It seems like a critical part to me.              

Thanks for any input.

Edited because I can't shpeelllll.



     
   

On a 20" barreled rifle, leverage is in your favor.

I'd take off the top handguard and apply pressure to the gas tube there rather than inside the upper. A little pressure goes a long way in correcting any gas tube/carrier key alignment problems.

Go slow and verify your progress with the bolt-less carrier test.

Thanks for responding Greg.
 
I will try bending the gas tube if there is no other way to fix it. Is it even necessary to fix, will it cause any malfunctions. What causes the gas tube to be canted, I thought it might be the snap ring behind the delta ring.    

Edit, I don't think it's the snap ring anymore, I think it might be the barrel nut.

556Cliff,

If the barrel nut is not correctly aligned with the cloverleaf for the gas tube the gas tube will be misaligned with the carrier key.

Pull the upper off the lower, the handguards off the upper, the gas tube roll pin from the FSB, and the gas tube from the rear of the FSB. The front of the gas tube should point directly at the hole in the FSB. If it does not then the barrel nut probably needs to be rotated.

Thanks Tweak.

Is it hard to move the barrel nut, and how do I do it?

I also think it might be the front sight base. When I look down the receiver and barrel with the carry handle removed, it looks slightly canted to the right, it could be an optical illusion I don't know, but it could be causing the gas tube to hit the side of the barrel nut, and it is hiting the right side, But the barrel nut is perfectly aligned with the X shaped hole, or cloverleaf in the upper receiver. could it be a under indexed barrel, you never know with Bushmaster? I have not shot it yet so I don't know if that is the problem, and still is it even a big enough problem to worry about? Also could shooting it heat up the gas tube enough to warp it while in the carrier key to stay centerd?

You guys are great help!        
               
Thanks, 556Cliff

Edit, I accidently hit the submit button three extra times,
how do I fix it. Thanks          

btt

First zero your rifle (50yds preferred). Note any crazy windage adjustments on the rear sight. If there are none, then the canted FSB should be ruled out.

After firing 200 rounds or so, check to see if there is still friction between the gas tube & carrier. Maybe the rifle just needs to be broken in.

Thanks Gregw45,

I will do that. I'm just waiting on cleaning supplies. I can't stand the wait.    

I suggest you first decide whether the front sight base is incorrectly aligned, before doing anything to the rifle. If it is, I'd send it back to Bushmaster because that's not something that is easily corrected by the average person. If the base is installed correctly, though, and all it takes is a little tweaking of the gas tube, that's not difficult to do.

With a barrel wrench, receiver blocks and vise. It's not difficult with the right tools.



The flared end on the gas tube will wear down faster than it should and you'll start getting short strokes.

Send it back to BFI, I hear they have excellent customer service.




That would be the "delete" key above your every post.

Thanks guys,

When I'm sighting in how many cliks of windage to the left or right is to much, and to get the mechanical zero windage centered before I sight in do I point the windage knob pointer straight up, or do I ignore the windage knob pointer and just go by the widage scale? shouldn't mechanical zero windage be centered on the windage scale by pointing the windage knob pointer straight up?

thanks, 556Cliff        

I'm assuming you have A2 style iron sights on the rifle. There should be an index line on the top center of the large aperture. When that index line is centered on the windage scale on the rear of the rear sight base the sight is mechanically zeroed for windage.

With a 100 yard zero on a rifle your windage should be within 12 clicks +/- 5 clicks of center wind.

So if it's off the center windage mark by more then 5 clicks I have problems?

I have A2 sights on a removable carry handle. So I should ignore the windage knob pointer, and it shouldn't matter if it's pointing straight up, and I should just center mechanical windage on the windage scale?
         
If I just use the windage scale to center the mechanical windage what's the point of the windage knob pointer, the thick mark on the windage knob.      

Thanks Tweak
   

No, if it's off of center wind by up to 17 (12+5) clicks it's OK. 18 clicks is NOGO for rifles when zeroed at 100 yds. 12 clicks plus or minus 5 clicks.

Yes, just center the index mark on the large aperture along the windage scale on the rear sight base. Think about what you're asking, the index can be up and the ap can be one complete rotation away from center. Depending on who made the parts and who assembled them the knob may not even point up when the ap is centered.

Great question about the windage knob pointer. I dunno, there's nothing I can see in the milspec that mentions its use. I do have a dim and possibly faulty memory of uppers being rejected for testing bc the "R" and the windage index weren't pointed up. Never did figure that one out but we took off the offending knobs, turned them 180 and reinstalled them. Like I said, the spec doesn't mention the index, least anywhere I've checked. "7 complete rotations" "free from binding" yada yada.

Looking at my Colt the ap is centered and the index is up.

Thanks Tweak,

That's some confusing sh#t. My windage knob pointer is pointing straight up and the index mark on the large AP is only 1 or 2 clicks from center on the windage scale. So should I just leave it alone, or should I adjust it the two clicks to center and ignore where the windage knob pointer is pointing.

Thanks, 556Cliff  

I would say it is all academic whether the index mark and windage scale line up since the final resting place of your rear aperture will be determined by where the bullets hit the target.  That said, to mechanical zero the rifle, the rear aperture should be centered on the windage scale, and if the index mark doesn't line up, forget about it.  If it bothers you take off the knob and re-index it.

I have an old 16" BM with excessive windage to the right, 18 clicks to be exact.  I never sent the rifle back in to be fixed since it really nevered bothered me.  The gas tube was not exactly centered in the rifle and as a result, it has worn down more on one side.  Haven't really had any reliability issues with it, but I do feel it may not be getting as much gas to the bolt as it could.  If I had to do it all over again, I would have made sure my gas tube was properly aligned before shooting my rifle.

Now shooting a few rounds through the rifle is not going to ruin your tube or rifle if the gas tube is not properly aligned.  It would probably take over 500 rounds before you started to see any effects of the misalignment.  Anyhow, it is not difficult to adjust a gas tube, even if the front sight base is canted, especially on a 20".  The main limiting factor is an improperly indexed barrel nut, but even if that is off a little, you can still get the gas tube to align properly.

The following is how I have adjusted tubes in the past, may not be the best way, but it works for me.  First of all, you must know what to feel for to know that the gas tube is properly aligned.  Field strip the rifle removing the bolt from the carrier.  Reinstall the carrier by itself back in the upper and push it forward.  If the gas tube is properly aligned, you should feel a very slight bit of resistance when the key contacts the tube and then slight friction as the key slides over the tube.  When pushing the carrier into the upper, wiggle carrier from one side to the other and see if you get more resistance if the key is on the right side of the receiver compared to the left side.  If more resistance is encountered on one side, bend the tube accordingly so that resistance is the same no matter where the key is located in the receiver.  This goes for up and down alignment as well.  Having a tube that is aligned side to side but not up and down will lead to the same issues.

As far as how to go about bending the tube, on a 20" you can try to do it the way mentioned previously whereby you take of the handguards and use the barrel nut as a fulcrum pushing on the tube in the opposite direction that you want the end of the tube to move in the receiver.  On carbines this doesn't work so hot and you are generally better off trying to bend the tube at the end, inside the receiver.  Any thing that can be used as a wedge or a lever will work, perferably something made of plastic.  For me, the end of a toothbrush works pretty well.  The main thing is to go at it slow, repeatedly checking alignment as you go so that you don't over bend the tube one way or the other.

Once the same amount of resistance is felt when the key is to one side or the other as well as up and down, your rifle will be good to go.  If the tube at this point doesn't look centered in the rifle, don't sweat it cause it doesn't matter, it only needs to be aligned with the carrier key.  Hope this helps.

[wow] Thanks for the detailed post jason_h.

If it ends up being the front sight post I'll reindex the barrel my self, or I will send it back to Bushmaster. I have waited four years to get an AR15 so a few weeks won't hert me. I'm still waiting on cleaning supplies from Bushmaster, that is driving me nuts.

I also ordered the Bushmaster armorer's video is that any good?  

Thanks guys.
 

Hello again,

I got tired of waiting on cleaning supplies so I E-mailed Bushmaster techsupport again. Here is what I wrote.

________________________________________________

Hi, I have a new Bushmaster XM15 rifle and the gas tube is not perfectly aligned with the carrier key. How do I fix this without bending the gas tube? I E-mailed you guys about a week ago and you told me to bend the gas tube with a screw driver to get it to line up with the carrier key, but I want to find the source of the problem. So I'm asking you to tell me what are the different reasons that cause the gas tube to be canted, and how do I fix it? I currently think it could be the front sight base. Thank you for your time.
________________________________________________

Here is what thay wrote me back.
________________________________________________

You can remove the gas tube and barrel nut to see if the nut was hitting on one side of the gas tube then reinstall the nut and gas tube to see if it lines up. The sight base would not affect the alignment of the gas tube.

Thank you.
________________________________________________

Now, is what thay are saying about the front sight base not affecting the alignment of the gas tube corect? I don't buy it.

thanks guys,    

cliff,
I just boxed up my mforgery bushy upper and sent it back to Maine last tuesday.I had basicly the same problem ,front sight was canted and 20 clicks of right windage was neccesary to zero rifle.I called bushmaster cust. service and they told me to send upper back. five to seven day turnaround! This is my first AR and its killin me I only had the gun three days when I boxed the upper .The way I see it is I have waited this long for my bushy another two weeks aint gonna kill me to have it right.If I were you I would send it back if your not satisfied
              mike    

Thanks for the reply Mike.

It would be the same for me, I lived without my AR for so long it wouldn't kill me to send it back to Bushmaster for two weeks to get it fixed. It just sucks that my first AR isn't perfect.  
       
Thanks, 556Cliff

Hey guys I shot my rifle yesturday, I put 60 rnds of Q3131A through it, no malfunctions of any kind. I shot a pumkin filled with water at 15 feet it exploded, I shot some milk jugs at 50 yards they really exploded, I shot a bucket full of sand at 50 yards it put two shotgun slug size holes through it and the coolest thing I shot at 50 yards was one of those spin-around steel targets, my first shot hit it, when I looked at the target the hole looked like a 30 cal went through it, both sides of the hole look like an exit hole. It was so cool!!!!

The only reason I shot it was because I couldn't wait for cleaning supplies any more. I didn't even adjust the sites, the windage was centered and the rounds hit were I was aiming, I wasn't on sand bags but I was sitting and I was holding it prety still, I don't think the sight base is crooked any more. It must be the barrel nut.      

                 
Thanks guys, 556Cliff    

Or... the barrel nut is OK, and the gas tube was simply bent during assembly.

[;)]

I haven't tought about that, thanks.

I would still like an answer to this question, any help would be great.

Thanks 556Cliff

btw 220 rounds with no cleaning and the factory 10 round mag, still no problems.  

Edit I just got my cleaning stuff today. Woo Hoo!!! I cant wait to clean this thing!!!    

What question is that 556Cliff?

Well Bushmaster told me that the gas tube carrier key alignment can not be effected by an off center front sight base.Is this true?

Thats the question.        

Well, I'm not going to respond to bushmaster because I'm not exactly sure that's how they worded it.  However, I can respond to your wording of the question.

No, it is not true.  An off center FSB can effect the alignment of the gas tube, which could then cause the carrier key and gas tube to not align properly.

Thanks wyv3rn.

What I wrote is what thay said. I knew thay were rong.

Thanks 556Cliff  

Of course it's not true.

Well I was pretty shure that it wasn't true, I just wanted to be 100% shure

Thanks 556Cliff