Building my first AR.  Using an Anderson lower.  Once I start threading the buffer tube into the receive, it goes about 1 1/4 turns and then gets pretty stiff.  Doesn't appear to be cross threading, it just gets very difficult to turn.  I took it in to the place I bought it from and they checked it out and had no idea why it wouldn't thread the entire way and said they'd have their gunsmith look at it tomorrow but I'd have to pay $45.  I told them I didn't think having to pay for something that was out of my control was a good business practice given that both parts were brand new from their store and this happened on my first attempt at threading it together.  Curious if anyone has any ideas what could be happening and if I'm out of line for not wanting to pay to have someone check it out.  Thanks.

Are you lubing the threads? And no I do not think you are out of line for asking the place you bought the parts from to check it out. I would not pay $45 either.

Vince

Hey Vince, no I didn't lube them.  I was wondering about that.  I was following the instructions on a couple YouTube videos and they didn't mention it so I didn't do it.  Hopefully that's all it is.  Just seems strange.  Thanks.

Some can be a little more resistant to threading in than others, probably nothing wrong with it. If you have a strap wrench try that but I would not use an overly amount of torque to install it, it should go in.

Vince

Thanks Vince, appreciate it.

No prob, let us know how it goes.

Vince

Did the shop sell you an airsoft/low quality receiver extension? Quality parts made to specification should not require more than hand strength to thread together.

Check for any debris in the threads of both components. Lubrication is not normally required to install a receiver extension, but it won't hurt to use some, and good lubrication will help prevent galling.

What brand is the receiver extension?

If it will not screw in by hand something is wrong with one or the other.
Unless the receiver extension is a brand name I would suspect it first.
I would check the thread pitch and diameter, maybe someone would do that for free and maybe not.
That the place that sold the parts won’t says everything I would need to know about them.
Take the RE back and get your money back and get a RE from one of the known sources on the web like Brownell’s.
It that does not fit contact Anderson.
The TM calls for the use of the mil-spec grease used to mount the barrel to the upper.
The TM also has torque specs for mounting the RE to the lower.
Utube is great for a visual aid if you know enough to know that the info is correct.

So you buy two components from an LGS, and they tell you the problem with their products that should work with each other...but don't...is going to cost you money?  I'd find another LGS when this is resolved.  And the $45 seems an odd service price for a problem that is most likely the cheaper of the two components...the extension.  A gunsmith is necessary for this diagnosis?  Seems like needing a full fledged physician to diagnose a mild sunburn.  Unless there's more to this story, this sounds like a fairly incompetent LGS.  Surely this shop has another Anderson lower and another extension tube to make a quick comparison to see which component might be defective or out of spec.  Of course, it's possible the poster could have misthreaded or boogered up the threads in one or both of the components, but that too should be easily diagnosed by the counter man without needing a PHD gunsmith.

On the lubing issue, I always use a small amount of antiseize on the extension.  Working in automotive, motorcycle, and even bicycle environments, a little antiseize on aluminum and many steel fastener threads has saved a lot of heartache and gnashing of teeth.

If the castle nut screws onto the tube, their must be something wrong with the threads on the lower.  Does the castle nut screw all the way on the tube?  Is there any burs or grime/ dirt in the threads on the lower?  Don't take this the wrong way but are you screwing the castle nut all the way on and pushing the end plate all the way to the back of the tube before screwing it on?  If not, it can bind and will not let you screw the tube into the lower.

When your screw the tube in to where it gets tight and back it off is anodizing coming off of the tube threads?

Nope.



Castle nut screws all the way on the tube.  No visible burs/grime/dirt in the lower.  Yeah, the nut and end plate are all the way to the back.



It's ATI.

Not sure if it's related, but the buffer tube kit is commercial instead of milspec.  When they sold it they said it didn't matter, only for the buttstock.

ATI seems inordinately proud of their 6061T6  mil-spec RE.
There is a question of the suitability of 6061 T6 for a mil-spec diameter RE.
The Brownell’s 7075 T6 mil-spec RE is around $26 and fit my lower correctly.

Get a proper 7075 RE and try it. I'd bet the ATI part is bad over the lower.

Try more tubes.  My bet is on out-of-spec tube threads.

Just got a call from the gun shop and turns out the buffer tube was the problem.  He tried another one in the package and it threaded on without a hitch.  Talk about a random defect!   At least I know I won't be charged!
Thanks again.

Great glad you got it straightened out. Now carry on with that build, and go with a MilSpec buffer tube.

Vince

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