Broken Upper Receiver! DOH!!

[oldrifle]

Last night I decided to change the barrel on my AR to the new CMMG medcon middy that I bought to replace the Armalite hbar that was on there. The recommended minimum torque is 30 ft. lbs. and the max is 80. I decided to start at 30 and work my up to maybe 50. I set the wrench to 30 and cranked down on the nut. I should mention the upper receiver is in my table vice with the PRI vice block (http://www.midwayusa.com/viewproduct...tnumber=878754). The nut wasn't budging very easily so I gave it a big crank thinking the torque wrench would do its job and click if it hit 30 pounds. I should also mention this is a brand new torque wrench that I just purchased at Harbor Freight.

When putting quite a bit of force on the torque wrench I heard a loud POP and saw a puff of what looked like gray smoke (probably aluminum dust) and the smell of scorched metal. I could see the upper was cracked. I took it out of the vice block and it looked like this:



This is an Armalite upper... not some cheap piece of crap -- which is why I was so shocked this happened. Right now my concern is whether I was using the right vice block for the job and whether the upper receiver can take 30 ft. lbs. of force when held by the takedown pin holes or whether my torque wrench wasn't function properly and I was applying much more than the 80 ft. lb. maximum. It looks like I essentially tore the upper apart.

[nrakid88]

Damn, did you turn green before you cranked down on her? Just kidding, I am willing to stake a small bet that there was a imperfection in the cast, which led to this failure.

[Noobert]

This broken upper can now join that broken lower at the bottom of the pond

[mydogsmonkey]

maybe ask armalite what they would do

Ernest

[oldrifle]

Damn, did you turn green before you cranked down on her? Just kidding, I am willing to stake a small bet that there was a imperfection in the cast, which led to this failure.

Haha, no but I put a lot of force on it... not an extreme amount of force... but then again I was counting on the torque wrench to tell me when I reached the 30 lb. setting.

You think I should call Armalite and see if I can send it in to have them check it out?

[oldrifle]

and you do know that a "click-type" torque wrench only "clicks" at the preset torque.. it doesn't actually prevent you from continuing past the setpoint and doing this kind of damage..

I do know that. I was applying force in a controlled way so that as soon I heard the click I would remove force on the wrench. I've used torque wrenches before when working on motorcycle engines so it's not like I've never used one before. This is the first one I've ever owned. I understand about the Harbor Freight thing. It's probably a good idea to go buy a higher end one to be safe.

[Ed_Hazard]

Haha, no but I put a lot of force on it... not an extreme amount of force... but then again I was counting on the torque wrench to tell me when I reached the 30 lb. setting.

You think I should call Armalite and see if I can send it in to have them check it out?

Might be worth it. They could check it out and would help rule out failure on their end (manufactureing/QC issues).

[oldrifle]

Might be worth it. They could check it out and would help rule out failure on their end (manufactureing/QC issues).

I just got off the phone with Armalite. They said they've never heard of this happening when using the proper vice block, only when people put the receiver directly into the vice (who does that?). I told him exactly what I did and he said that's really strange and that I can send it in if I'd like so they can take a look. It doesn't sound like they're willing to replace it but at least they'll take a look and see if there was a defect. In the meantime I just ordered a new DPMS upper housing for $95.

[Nick1236]

This broken upper can now join that broken lower at the bottom of the pond

I see what you did there

[tonelar]

wouldn't the crack be on the opposite side of the lug with your force being applied counter clockwise?

or am i mis-reading your post and you were installing as opposed to removing your barrel nut (delta ring)?

[nrakid88]

I just got off the phone with Armalite. They said they've never heard of this happening when using the proper vice block, only when people put the receiver directly into the vice (who does that?). I told him exactly what I did and he said that's really strange and that I can send it in if I'd like so they can take a look. It doesn't sound like they're willing to replace it but at least they'll take a look and see if there was a defect. In the meantime I just ordered a new DPMS upper housing for $95.

You should strip it before you send it out, Armalite may not send it back to you, and it's always nice to have extra parts. (I am a hoarder for firearms parts)

[kendog4570]

Ouch!
It looks like the block you were using is to be a "third hand" for installing sights and whatnot, and not for tightening the barrel nut, even though Midways' site has a testimonial for just that. It broke where you might expect it to, judging by the holding method of the block(through the pin bosses). This type will hold it a little better for that task.

http://www.brownells.com/.aspx/pid=22385/Product/AR_15_M16_UPPER_RECEIVER_ACTION_BLOCK

I think you could also clamp the barrel in a barrel vise and tighten the nut with the receiver hanging free. I know the specs say 30-80 ft lbs, but it isn't always necessary to stick to that like glue. I have put many an upper together with a strap wrench and blue loctite, and they dont come apart until I want them to. Each one is different and you have to "listen" to what it's telling you when to do a preliminary fit up.
AR's are a modular wonder, but there is still some old-fashioned gunsmithing involved in building them.

[oldrifle]

You should strip it before you send it out, Armalite may not send it back to you, and it's always nice to have extra parts. (I am a hoarder for firearms parts)

Yes, I certainly will. I need the parts for my new upper anyway. Thanks!

This type will hold it a little better for that task.
http://www.brownells.com/.aspx/pid=2...R_ACTION_BLOCK

I think you're exactly right. I don't think the vice block I used holds the receiver sufficiently for barrel changes. I'll grab one of the ones you suggest. Thanks!

[oldrifle]

wouldn't the crack be on the opposite side of the lug with your force being applied counter clockwise?

or am i mis-reading your post and you were installing as opposed to removing your barrel nut (delta ring)?

I was tightening the nut on the new barrel. I was twisting it to the right and the receiver cracked on the left side.

[TurboAR]

Ouch!
It looks like the block you were using is to be a "third hand" for installing sights and whatnot, and not for tightening the barrel nut, even though Midways' site has a testimonial for just that. It broke where you might expect it to, judging by the holding method of the block(through the pin bosses). This type will hold it a little better for that task.

http://www.brownells.com/.aspx/pid=22385/Product/AR_15_M16_UPPER_RECEIVER_ACTION_BLOCK

I think you could also clamp the barrel in a barrel vise and tighten the nut with the receiver hanging free. I know the specs say 30-80 ft lbs, but it isn't always necessary to stick to that like glue. I have put many an upper together with a strap wrench and blue loctite, and they dont come apart until I want them to. Each one is different and you have to "listen" to what it's telling you when to do a preliminary fit up.
AR's are a modular wonder, but there is still some old-fashioned gunsmithing involved in building them.

I beleive he is correct on this. i have removed the barrel nut on 20 or so uppers with this type holder, Never a problem.