How much wear does repeated upper disassembly put on an upper receiver?

[zukiphile]

One of the ways I appear to have a screw loose is my habit of letting stray thoughts about upper configurations turn into built uppers. My reasoning is that building a new upper doesn't leave me with a bunch of spare parts and avoids the stress of reassembly on an upper. My uppers are Andersons (so they aren't supremely expensive items) and my assembly method is the three cycles of tightening with the final cycle involving torque to 80 ft lbs.

Am I wrong?

Has anyone here disassembled and re-assembled an upper so often that the threaded portion wore out or broke?

[Scorch]

80 ft-lbs? No wonder you're worried about the threads!

[bedlamite]

You need to revisit your assembly procedure.

[zukiphile]

80 ft-lbs? No wonder you're worried about the threads!

You need to revisit your assembly procedure.

I would be happy to be better educated on this, but the last link shows the final torque value to be limited to 80 ft lbs.

[ed308]

Are you saying 80 lbs or torque on the barrel? Thats the high end of the torque limit. It makes it really difficult to remove the barrel if needed in the future. I usually torque barrels to 30-40 lbs. or a little more and never had any problems. I always use AeroShell 33MS grease on the threads which helps as well.

But to answer your question, I've never seen the threads wear out on a upper.

[zukiphile]

Are you saying 80 lbs o[f] torque on the barrel?

I start with 30 lbs on the wrench, turning until it clicks. I loosen and proceed to 35 until it clicks. Repeat at 40 lbs, then set it at 80 and go for correct alignment.

[Bartholomew Roberts]

That's the correct procedure. You are rarely going to hit 80lbs that way. I think people are confusing your setting with the actual torque applied.

As far as wearing them out, I've never seen it. Even in the military when I would occasionally draw a rifle with an XM16E1 marked lower some 30 years after the M16 was adopted. Maybe some former military armorers could chime in?

[bedlamite]

I start with 30 lbs on the wrench, turning until it clicks. I loosen and proceed to 35 until it clicks. Repeat at 40 lbs, then set it at 80 and go for correct alignment.

80 is the absolute max. You should get alignment before you ever reach that. I don't think I've ever had one torqued over 60ft-lbs.

[zukiphile]

Originally Posted by BR

I think people are confusing your setting with the actual torque applied.

I'll take the blame for that.

Originally Posted by BR

As far as wearing them out, I've never seen it. Even in the military when I would occasionally draw a rifle with an XM16E1 marked lower some 30 years after the M16 was adopted. Maybe some former military armorers could chime in?

I suspected that the wear I was saving might not be a big deal. Below average foresight on this point leaves me with too many built uppers; maybe I can slow my affliction by rebuilding just one until it gives up.

I can't be the only fellow on the planet dumb enough to have had this problem.

[HiBC]

I would assume as long as the hard anodizing is unaffected the threads are not worn. Actually,intact anodizing on the whole receiver says a lot.
It would take some fancy finite element analysis and the knowledge to use it to venture a guess on distortion,or maybe some dial indicator checks.

The one concern I have with upper receivers I have used more than once might be the receiver face distorting.That is the foundation the barrel extension rests on.If its not true and flat,even with it tight it might wobble.

One of the lapping mandrels very lightly used would show high spots.

[Ibmikey]

Having built hundreds of AR's and using anti seize on the receiver threads along with torque values in the 35# range during final assembly I doubt that the threads will suffer degradation in my lifetime. I have never had to use heavy torque to line up a barrel nut.

[Mobuck]

I never get close to 80 ft lbs.
But be advised that a steel nut turning against aluminum threads can/will lead to thread wear/stretching/damage.

[zukiphile]

Originally Posted by ibmikey

I have never had to use heavy torque to line up a barrel nut.

You've led a charmed life, I'm doing it wrong, or both.

I had one hard case that wouldn't make minimum poundage on one tooth, but wouldn't make it to the second tooth on 80 pounds. I bought a shim.

Originally Posted by Mobuck

But be advised that a steel nut turning against aluminum threads can/will lead to thread wear/stretching/damage.

Undoubtedly, but I think that is properly part of the process, at least initially. Threads stretch a bit and the face if the receiver mates to the barrel.

[rickyrick]

It will change every time. How long until until the reciever is unusable, who knows.

I would say if there were any cases of people destroying their uppers, we would have lots of pictures here.

[marine6680]

You guys are lucky... I have hit 75-80lb ft to get alignment.

But I also us my torque wrench properly, and use the formulas for torque using an adapter that increases the length... Like pretty much every barrel wrench does.

If your barrel nut wrench extends the wrench 2in, at 80lb ft actual applied torque, your wrench will read 12lb ft low... So your wrench clicks at 68lb ft, but you are really applying 80 lb ft.

Every instructional video I have seen, does this wrong, and does not take this difference into account.

Mil spec type barrel nuts are the only ones I have had to do this with though. Others seem to line up easier.

[MarkCO]

I have an upper that has been rebarreled 6 times. close to 100K through it, and still going strong.

I typically torque to 80-95 ft-lbs, with anti-seize and when new, torque and release 3 times to 40 ft-lbs. With 7075 receivers which are 40% stronger than the 6061s. You will find a lot of guys who build precision ARs with higher torque levels to minimize the thermal drift.

[rickyrick]

My last was the trickiest. An Aero Precision keymod upper, had to do shims to get it to all line up.

[Mobuck]

I question the "why?" of continually swapping barrels on a single upper. I just bought a box of new uppers @ under $50 each delivered to my porch. Why challenge the dinky little aluminum threads over and over?

[zukiphile]

Originally Posted by Mobucks

I question the "why?" of continually swapping barrels on a single upper. I just bought a box of new uppers @ under $50 each delivered to my porch. Why challenge the dinky little aluminum threads over and over?

It's a fair question, but the motivation doesn't pertain directly to the cost of the uppers. I have more assembled uppers than I want.

ARs have gotten me into a bad habit. I think about the merits of a configuration. Curiosity drives me to shop and figure out the cost of that configuration. The shopping leads to buying. Buying leads to assembling, testing, and getting good accuracy and reliability out of the new project. When it's all squared away, I store it and start thinking about other ways to do it, which starts the next project.

I don't know what you would call that hobby, but I wouldn't call it "shooting" exactly.

[Ibmikey]

Zukiphile has a good point, every time my little brain determines there are new and exciting psparts released for the AR weapons it seems I must build another. I do not go the intelligent route however, and instead of just building uppers I built whole rifles. Now with almost forty AR's in the racks I find I shoot less than half dozen on a regular basis ( one of those being my favorite S&W Sport).
Still the challenge of a new assembly has me searching part by part for the items to suit my current needs, sure I can buy an assembled rifle cheaper but that is not the issue.

[zukiphile]

Originally Posted by ibmikey

... I find I shoot less than half dozen on a regular basis ( one of those being my favorite S&W Sport).

My defect involves me seeing the last one I built as my favorite; that's the one that goes to the range, at least until I build the next. I have too many scopes too, but now something knocked loose the idea of an iron sight build, so I am waiting on parts for that.

[rickyrick]

Zukiphile,

That's exactly why I put myself on an AR diet. I was building them and not shooting the others. There's one I haven't even put a bullet in yet too lol.