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Old December 21, 2018, 07:07 PM   #1
ks_wayward_son
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First AR build...real humdinger

Hey everyone. Well, been working on my first AR build for quite sometime, and not going according to plan. Was hoping everything would sorta fall into place. Uhhhhh, not so much. (Yeah another one of "those posts."

I've been trying to install a YHM diamond rail (outdated, I know...but still looks cool to me). I've done the torquing of the barrel nut to 35...loosening, torquing....repeat repeatedly and no matter how many times I try to torque up to about 80 ft lbs can't line up the gas tube with the barrel nut and extension. Almost gets there but not quite. I don't want to over torque either. In the process sorta jacked up my barrel nut a little but thankfully the rail still threads nicely regardless, so got that going. Anyways, I was considering using shims like these to get the job done and move on.

Shims:

https://www.amazon.com/FieldSport-Fl...rrel+nut+shims

Any cons to using these, or just go for it?

Also, If I chose to replace the barrel nut some day, does anybody have any potential replacements that might work? YHM barrel nuts like the one that goes with the Diamond series don't seem to be manufactured anymore, besides when I can find one its aroud 35.00, I know quality costs. Not sure what the thread pitch is though. It would be similar to this:

https://www.opticsplanet.com/yankee-...-yhm-9483.html

Wonder if one of these knockoffs would work:

https://www.walmart.com/ip/Barrel-Nu...Rail/564637010

Dang, this build has been a real learning process, just wish it hadn't happened right out of the gate, but so it goes.

Thanks for any advice/comments.
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Old December 21, 2018, 08:00 PM   #2
Omaha-BeenGlockin
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Did you use the "proper" grease? ---yes it makes a difference

Things don't necessarily have to be torqued to 80lbs---that's just the max-----35 to 80 is the range if I'm remembering right----probably better off closer to 80 than to 35.


I've taken apart factory rifles that were barely tightened up and worked just fine.
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Last edited by Omaha-BeenGlockin; December 21, 2018 at 09:07 PM.
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Old December 21, 2018, 09:04 PM   #3
Nathan
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No cons I know to using steel shims. Torque is 30, then raise until gas tube aligns, not to exceed 80.
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Old December 21, 2018, 09:51 PM   #4
TruthTellers
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Will the nut index with the gas tube at any torque between 35 and 80? There's no need to go to 80 ft/lbs if the nut indexs fine within that spec range. My build I did with an AR Stoner FF guard was a tough one as it didn't have as many indexing spots and I had to buy shims to get it done. 30 ft/lbs did index fine, but I wasn't comfortable running it at that and managed to get 40 ft/lbs after a combination of shims were installed.
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Old December 21, 2018, 10:41 PM   #5
rickyrick
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80 is where you stop trying, not a goal. Should line up after the initial torque and before the 80lbs
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Old December 22, 2018, 06:55 AM   #6
imashooter
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Grease the nut and receiver well.

Lightly grease the barrel extension to include area behind alignment pin.

Install barrel nut.

Torque to 30/35 ft lbs. Back it off.

Repeat this step 2 additional times.

Take it up to approx 50lbs or so (+ or -).

If it still doesn't align, shim it. Shim kits include a few shims of assorted thickness.

Sometimes it might take 2-3 attempts to get it right.

Remove excess grease from between barrel nut and rcvr.

It's not uncommon where you only need another 1/16" or so rotation for alignment yet to get there from a low torque value can put you well beyond 80lbs. Much easier and smarter to shim.
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Old December 22, 2018, 07:05 AM   #7
Mobuck
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I don't think I've ever even come close to 80 foot pounds of torque on a barrel nut and NONE have come loose.
I've had to use shims a couple of times but I'm more likely to try a different barrel nut (or even a different upper)and only use shims if none of the barrel nuts/upper combinations on hand give me what I want.
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Old December 22, 2018, 08:26 AM   #8
kymasabe
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The whole idea of clocking the barrel nut and shimming irritates the bejesus outa me. There are many handguards out there that don't require it anymore, so I build with those.
Aero atlas s-one
Odin works ragna
Dirtybird smrs
...and even a cheap $35 ebay chinese m-lok handguard.

I lube with aeroshell, tighten to 30, loosen, repeat 3 times, then final torque to 50.
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Old December 22, 2018, 10:07 AM   #9
ks_wayward_son
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Went ahead and ordered the shim kit. Regarding the shims, is it alright to stack them if I need to or just use a different thickness?

The procedure I used initially was that I threaded the extension with some Lucas Red N Tacky anti seize. This is the stuff I'll probably be using to grease the bolt carrier group and stuff too, so I had it on hand.

When I hand-tightened the nut, it was just shy of an indexing slot. Probably 15 to 20 or maybe less would have been spot on. I knew it was going to be problematic right then. Torqued to 30-35, backed off, once again to 30/35, backed off. Then I tried increments of 45, 65, 75 to almost 80 and didn't get alignment. I tried the whole procedure a few times. And decided I'd better try a different route.

I started to sweat a little when I approached the 80 ft pounds torque limit and didn't click over. Decided to say enough was enough.

Plus, I admit I am not the stoutest fellow (5 ft 8 and 145lbs) so breaking the 75 + torque for me was a real chore and had to use a 1/2 ratchet set on counter clockwise in conjunction with the barrel nut wrench. Therefore, I REALLY dont want to have to approach the 80 pd mark to save frustration.

Already thinking about next build, will probably be using a simpler rail and barrel nut combo, but just wanted to use the Yankee Hill for this one because it caught my fancy.
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Old December 22, 2018, 08:34 PM   #10
ed308
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I’ve only needed to torque one barrel to 80 lbs. It was an AR10 and I had to go that high to get the barrel tight enough where it wouldn’t come loose. Had to use shims to get it where it would index too. It is easier to index with shims. 30-40 lbs. is usually good for a AR15.
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Old December 25, 2018, 11:22 AM   #11
Metal god
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I went a different route . I’ve only had a indexing issue once . Instead of using shims I lapped the upper back to get that extra movement in the nut . I have the lapping tool though but if I didn’t , I would have used shims
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Old December 25, 2018, 08:44 PM   #12
ed308
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I went a different route . I’ve only had a indexing issue once . Instead of using shims I lapped the upper back to get that extra movement in the nut . I have the lapping tool though but if I didn’t , I would have used shims.

I usually lap all my receivers. And lapping is a great way for getting the nut to index. But in my case, the upper was a Aero Enhanced upper which can't be lapped but any current lapping bar to my knowledge.
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Old December 27, 2018, 05:24 PM   #13
bfoosh006
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I am also a big fan of lapping the upper receiver face.

Every barrel I have installed, and then reinstalled after lapping, has shown an improvement in precision and is generally more consistent in group size from a much larger variety of factory ammo.... ( Far less fliers. )
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Old December 27, 2018, 11:11 PM   #14
rickyrick
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I lap mine because it technically makes sense. The receivers I have lapped so far had high spots initially.
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Old December 28, 2018, 01:47 AM   #15
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Yup, nearly every forged receiver is going to have a high spot. Regardless of which forge mark it has, or where it come from- it will likely have a high spot in the 12 to 3 o'clock area as you look at the face with the rail to the top.

With billet receivers, if it has a high spot at all, it could be anywhere.

I remember showing this to a shop owner in Perryton, TX. He swore up and down that all of his receivers were straight and of good quality. I told him that I agreed that they were undoubtedly of good quality, but I stood 3 of them on end, and sure enough they all had a vague resemblance to little leaning Towers of Pisas.
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