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Posted: 12/24/2011 12:24:07 AM EDT
I'm building a rifle, all's going well until I put the BCG and charging handle into the upper receiver, slide in the pivot pin, and try to close the two receivers. At that point, the rear of the BCG actually hits the lower receiver (by the threaded part), preventing the receivers from closing. i realize that about 1/8th inch of the bolt carrier is sticking out the rear, and by looking at pictures on the internet, i believe the bolt carrier is not forward completely.

I'm not sure what to do here....
Link Posted: 12/24/2011 12:38:20 AM EDT
post pics
Link Posted: 12/24/2011 12:38:43 AM EDT
Make sure your bolt is assembled correctly, and push it all the way in until it locks into the chamber?
Link Posted: 12/24/2011 12:53:01 AM EDT
Check your gas tube, it might be out of spec binding on the gas key.
Link Posted: 12/24/2011 12:57:47 AM EDT
[Last Edit: 12/24/2011 12:58:13 AM EDT by statuskuo]

as you can see, the back end of the bolt carrier is hitting the buffer. even with the buffer depressed, the bolt carrier hits the lower receiver. i believe this is because the bolt carrier isn't all the way forward. i could be wrong though.

as far as i can tell the bolt carrier is assembled correctly..
Link Posted: 12/24/2011 1:26:57 AM EDT
How hard did you push the BCG?

I think you may just need to ensure the BCG is fully in/locked.
Link Posted: 12/24/2011 1:42:03 AM EDT
Looks like your charging handle isn't all the way forward. Push the Ch forward or push the BCG in all the way.
Link Posted: 12/24/2011 2:20:47 AM EDT
Did you extend the bolt all the way before you slid it into the upper?
Link Posted: 12/24/2011 2:35:28 AM EDT
Originally Posted By KBAD:
Looks like your charging handle isn't all the way forward. Push the Ch forward or push the BCG in all the way.


Good eye.

Try what he said first OP.

You can see the handle isn't locked into the upper, lock it and you'll have some more room. If the handle won't lock something else is wrong.
Link Posted: 12/24/2011 8:34:37 AM EDT
[Last Edit: 12/24/2011 8:36:37 AM EDT by statuskuo]
thanks for the responses. It wasn't the charging handle.. its just in this pic that its not all the way forward. I've pushed both CH and BCG pretty hard into the upper.

check this out... the top picture is how much 'bolt' you see when its in my upper. the bottom picture is how much bolt you see when i compress it down all the way when its not in the receiver. so i feel like the bolt carrier can go in more, but somethings blocking it. and i was also wondering if the gas tube is too long and somehow getting blocked by the gas key.


Link Posted: 12/24/2011 8:47:41 AM EDT
Can you take a pic of the gas tube in the upper?

At first glance, it doesn't appear there is anything wrong with the position of the bolt in the carrier.
Link Posted: 12/24/2011 9:15:20 AM EDT
Check the bolt lugs,both on the bolt and the barrel extension that they mate to . You could have some chips or some kind of goo preventing them from mateing up.
You also need to check that the gas tube isn't hanging up (as others have said.

If you suspect the gas tube tap out the roll pin in the gas block and pull the whole tube completly out of there,now does the bolt close?

Have you got another bolt/carrier that you can borrow to try swapping it into your upper to narrow things down?
Link Posted: 12/24/2011 12:22:54 PM EDT
Can you post a pic of the bolt out of the carrier, and one taken down inside the bolt recess in the carrier?

Looks like the bolt is stamped MPI, what brand components?
Link Posted: 12/25/2011 7:07:50 PM EDT
I had this happen once ––-

My problem turned out to be the gas tube. I inserted the pin in the FSB "ahead" of the gas tube instead of through the pin hole. BCG would hang up at exactly the same spot. I swore it was something to do with the bolt.

Sparky
Link Posted: 2/2/2012 10:21:05 AM EDT
Originally Posted By sparky27:
I had this happen once ––-

My problem turned out to be the gas tube. I inserted the pin in the FSB "ahead" of the gas tube instead of through the pin hole. BCG would hang up at exactly the same spot. I swore it was something to do with the bolt.

Sparky


Thank you sparky, that did turn out to be the case. The length of the bolt extruding from the upper receiver seemed suspiciously like the length between the gas tube roll pin to the front of the gas tube.

I resolved this by taking out the gas tube roll pin, fitting the bolt first so that the receivers would close (so that the gas tube is in place), then punching the pin back in.

thanks for all your help guys!
Link Posted: 2/2/2012 12:11:56 PM EDT
Nice solve. I did the same thing on my first lower and had to undo/redo it, but looks like I'm late to the party - happy shooting!
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