AR help - please :)

daveyburt

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New upper installed by local reputable gunsmith.
First time to the range with it today.
Sighting it in. Put a couple on paper, and went to make safe to go check target.
Charging handle super hard to pull back....hmmm, maybe it'll break in.
Came back put two more on target. Charging handle even harder to pull back.
Hmmmm
Put one more on paper and cannot pull charging handle - totally locked.
Also wasn't able to pivot the upper open.

Let it cool down (not that it was that hot with 5 round thru it) while I sighted in something else. Was finally, barely, able to get the handle to pull back and remove the live round.

Packed it up and called it a (crap) range trip.

Now that I'm home I took a peek and see nothing of issue and the handle cycles normally.

A2 Sporter with new upper. Has cam pin for front pivot.
Any guesses?

thx!
 

Lxpony

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Sounds like your gas tube is misaligned and jamming up the charging handle.

With all due respect building an upper is stupid easy. Not sure why you didn't YouTube it and go about it on your own. Pm me if you want to chat. I've built many uppers and they all run 100%
 

citoriguy

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Are you running a flat top or did you try to attach a carry handle to the pic rail? You can screw those on too tight which makes getting the charging handle/BCG to work like it should.
 

Palladin

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I have the same problem a couple of weeks ago. At the tap the charging handle with a mallet to get it to extract the live around. I summed it up to not being lubed at the Locking bolt
 

daveyburt

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Factory brass ammo - LC headstamp

With all due respect building an upper is stupid easy. Not sure why you didn't YouTube it and go about it on your own.
I didn't want to get caught up in the parts decisions that go into it. I told the 'smith' "build it as you would build your own".
ETA - will inspect the tube interface - thx!

It was totally dry when I got it so, yea, CLP'd the bolt pretty well.

It is a flattop - no carry handle but did install a burris between the irons

Cool - so I'll bring a mallet (joking). You might be right. It was getting hung up fully inserted. Once I got it to budge, it ripped back like I was gunna yank it thru the back side of the upper. No friction for the rest of it's travel - just initially stuck.
I inspected the locking lug and saw absolutely no wear/marks on it's backside.

The Smith said he test fired it. Would one clean it DRY afterwards before giving to the customer?
I would think not but, possibly?
 
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enbloc

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I've seen some butt-stocks interfering with charging handle rearward movement. Any signs of light scratches on the area where the CH rides back over the butt-stock?
The new upper may be sitting a little low for your butt-stock configuration. Are you running an A2-style stock or a collapsible style stock?

Photo of configuration would help a lot...

Here is a gross representation of what I mean.

1605907235516.png
 

enbloc

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Also, take a look at your BCG-to-Buffer Retaining pin interaction. Anything look like dragging occurring on BCG groove or top of the pin?

1605908114053.png1605908296932.png

How's the Gas Key and Allen's look? Loose?

Is it well-staked and straight?

1605908454839.png
 
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gene

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The issue with the buttstock as indicated is a likely problem and sometimes an out of spec rung at the top where you tighten the locking nut.
 

teamRR

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Where are you located?

Run of the mill AR15's are really easy to figure out unless you have a pile of really oddball parts involved.
 

daveyburt

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just saw this..

How's the Gas Key and Allen's look? Loose?

Is it well-staked and straight?

View attachment 413495

Not 'that' well staked but, the tube interface has no wear - either on the gas key or tube so it looks and seems straight. -Just put a allen wrench on there and, they don't seem to budge. But, I'm gunna wait to hear back from the smith before putting a lot of force on them.

thank you!!

ETA - pristine on the front band back of the bolt lugs. Chamber lugs, as much as I can see look dandy.
 
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Besides a little on top of the charging handle shaft -barely perceptible (which seems par for the course), nothing -all looking new.

the action feels silky smooth in my hands right now.
Do you think possible mag and round interference pressure on bolt carrier?
Can you cycle rounds through it? Without firing pin installed.
 

daveyburt

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I'd still try swap-out of parts (one at a time).

Learning how to diagnose AR problems is (and will be) a very important skill in the future. Use this as an opportunity!

I'm a bit of a newb with them but, yea, I'm learning a lot right in this thread!
:)
 

enbloc

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I'm a bit of a newb with them but, yea, I'm learning a lot right in this thread!
:)
Good on you!, As long as you don't pull out any powertools... you should be safe. [smile]

First try your new upper on a known good lower, and see if problem persists...
 
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