help please...

[Jeff2131]

I found, during cleaning, that the barrel in my ar10 is loose! With the chamber open, i can literally twist the barrel with my hand and watch the barrel move slightly inside the chamber. If the barrel is slightly twisted the bolt lugs wont open to allow me to pull the charging handleback until i twist the barrel back into position. Not sure how this even happened. Now, i have never taken an AR apart this far so im in need of some advise. this is a dpms sass with an 18" fluted heavy barrel, free floating forend, quad rail, gas block and tube. I managed to partially unscrew the nut holding the forend on but it is not back against the upper. So....im assuming i have to twist the forend off the rest of the way. I cant because the gas tube is in the way. So i found the 2 set screws through the underside of the forend and removed them from the gas block. Heres where im stuck...the gas block wont budge. It should slide right out with the tube attached....correct? Do they put loctite or something in there to help hold it in place and is that why it wont slide out? Figured id ask rather then start trying to pry it out and.breaking something. Id prefer to avoid having to pay a gun shop. If i could just get the forend off i can inspect and tighten the barrel assuming the barrel nut isnt damaged or cracked. Any suggestions?

[tahunua001]

yeah that's bad... you'll need to remove the handguard and tighten the barrel nut. I think 60FTs is about the average for AR15s, not sure how tight AR10s need to be though.
I'm not sure how AR10s are attached but yes the gas tube should be slip pinned into place.

[Jeff2131]

From what ive been reading, 60ftlbs will be max for the ar10. I just need to figure oit how the heck to get this gas block.and tube out and ill be smooth sailing!

[FtrPilot]

I believe there is a roll pin in the gas block that holds the gas tube in. You should not have to remove the gas block, just the gas tube. There should be videos on youtube that show you how.

[Jeff2131]

Hmmmm....i did see a small roll pin but figured i didnt need to remove it because the gas block would slide off with the tube....ok. guess ill get my roll pin punches and pop that pin out and see if i can get the tube out.

[FtrPilot]

If the gas block is attached by hex screws, then it may be easier to remove the gas block.



I would still look at some videos.

[Jeff2131]

Yes, thats the gas block but its 2 hex screws not three...unless i missed one...ill have to double check.

[FtrPilot]

The picture is a sample...

I would try the hex screws first and see if the gas block will slide off.

[Jeff2131]

Nope...just 2 screws....heres a pic


http://s911.photobucket.com/user/jef...fo1pp.jpg.html

[tahunua001]

that's a low profile gas system, you do not have to remove them to remove the handguard.

[Jeff2131]

Ok, then how do i remove the hand guard. Sorry, as i said, ive never got this far into disassembly of an AR before.

[Mobuck]

Just so you know. If there's much rotational movement, the guide pin notch in the upper receiver may be damaged. If it is, you'll probably not be able to hold the barrel tight.

[FtrPilot]

From the pictures, it looks like you have a free float hand guard. Do you know who makes the hand guard?

[Jeff2131]

No, i dont know who makes it. I bought the rifle used and the work was already done to it.

[Jeff2131]

I got it apart. I DID have to remove the gas block and slide it down the barrel. The tube was preventing me from turning the forend off. Once.gas tube was out of the way i spun the forend off and then removed the barrel nut. It came off bg hand. Def should not be that loose. And the barrel was moving because the centering pin was almost broken in half. Ill need to replace the pin and that should do it. Does anyone know where to get those pins at? Got a link?

[Jeff2131]

Found one on brownells website but it says ar15....will it work for an ar10?

[FtrPilot]

Congrats on getting everything disassembled and finding your problem.

Personally, I have never seen or heard of an aftermarket barrel centering pin.

At this point, I believe you need to talk with a real gunsmith and see if there is an inexpensive solution to your problem. Or you may want to talk with a barrel manufacturer and get their opinion.

I will follow this thread to see what the more experienced bloggers have to say.

There is also a Smithy section here on TFL. You should start a thread in that section describing your problem.

My strong believe is that the person who installed the free float hand guard did not torque the barrel nut properly. You should have a discussion with the person you bought the gun from.

[HiBC]

If this was a factory made DPMS rifle,it would have been best to return it to them.If DPMS did that,they have a quality issue to correct.

If this is a semi-custom garage gun,someone screwed up badly.

That index pin should not bear the torque of tightening the barrel nut.

Inspect the notch in the receiver.If it is damaged,the factory would replace the upper.I would,too.

Did the pin fall out of the barrel extension?Thats the shouldered bushing with the locking lugs .If not,how will you get the pin out?

I do not ave exact numbers with me,but the barrel nut is lubed with moly grease,tightened to approx. 20 ft lbs,then torqued more till the gas tube hole is aligned.

You do not just put the upper in a vise.Some use vise jaws cut to fit the barrel dia.I had a problem with those,some match barrels ,the barrel extension may unscrew before the barrel nut is torqued.

I now use a splined wrench from Brownell's that goes through the upper like a bolt carrier and engages the locking lug recesses in the barrel extension.

You may have a scrap barrel extension.You do not just replace those.It has to do with thread indexing,headspace,etc.

IMO,it sounds like you need a stripped upper,and a new barrel assembly.

And,most important,the tools and skills and understanding to not muck it up.

You might try an Armorer's Manual.There are books and DVD's.Or,send it to DPMS.

[44 AMP]

If this were an M16A1 (or comparable AR15) then I would be absolutely sure of the procedure. I replaced quite a few barrels on them while working for Uncle Sam in the 70s.

But from the thread, I can clearly see the modern AR 10, with all those bells & whistles is a different kind of cat. Still a cat, but some things are different.

I can tell you, with the complete confidence of an aging memory that the M16A1 barrel nut should be tightened to 35-40 ft/lbs of torque, and then tightened until the barrel nut allows the gas tube to enter the receiver, and no more.

I would expect the AR 10 to be similar, perhaps with a different torque spec.

Call DPMS. Find out if they made the rifle, or if you have a "Frankengun" on their receiver. If they made it, they ought to be the ones to fix it. Since you got it used, it might not be a warranty covered thing. IF not, then you'll have to pay to get it fixed, so why not pay them? They might even be cheaper than a local smith. On the other hand, if you have to pay for shipping and the repair, and there is someone local, that might be more cost effective.
Even if you fix it yourself, you're going to have to pay for parts, anyway.

I believe that on the M16 class ARs that barrel index pin is pressed in. Don't know about the AR 10s, but it seems likely they are too. To replace that, you'd have to drill out the stub of the original pin to put a new one in, and that pin isn't a normally replaced part.

Good luck, and let us know how it works out.

[Jeff2131]

Rifle is fixed. I simply cut a put of steel and made my own indexing pun. Torqued barrel nut, reinstalled hand guard....good to go.

[Palmetto-Pride]

Just a word of caution you should definitely either check the head space yourself or have a gunsmith check it because if the barrel bushing wasn't screwed on correctly it may not be head spaced correctly, but hey its your eyes and fingers so do as you wish......

[Jeff2131]

Which piece is the barrel bushing?

[Ibmikey]

Normally the barrel extension (part bolt locks into) must be head spaced and timed to the gas port in the barrel. The index pin is installed as part of that process, get a competent (AR knowledgeable) gunsmith to check before firing.
One more thought, since the barrel extension was not moved just having proper vertical alignment should be GTG.

[Palmetto-Pride]

Which piece is the barrel bushing?

I meant to say barrel extension, but Ibemikey explained it pretty well. Like he said its how the head space is initially set and if you didn't screw the barrel extension back on to where the original pin lined up (assuming it was set correctly to begin with) you may have changed it. I know gauges are pretty common for a AR-15, but not sure about a AR-10 if I were you I would at the very least have the head space checked by a gunsmith that has experience with AR-10s. Good Luck!

[Jeff2131]

I should be good then. I didnt touch the barrel extension. It wasnt loose and checked out ok so i left it alone. Simply replaced the indexing pin, tightened the barrel nut, reinstalled gas block and tube, and reinstalled forend. Head space should be exactly the same.