Bolt locks shut and won't cycle

AR-15 » Troubleshooting

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[ARCHIVED THREAD] - Bolt locks shut and won't cycle

Posted: 7/23/2017 12:47:20 PM EDT

My most recent build is giving me fits.
The bolt locks shut. And I mean LOCKS.
I have to use a mallet to get it to unlock.
It locked up the first time I fired it. It locks up when cycled with a dummy round.
I changed out the bolt with another rifle. Still locks up.
Ideas?

Posted: 7/23/2017 12:51:08 PM EDT

[#1]

Did you change the bolt or bolt carrier? Have you checked your gas tube alignment and your barrel extension? Pics would help

Posted: 7/23/2017 1:14:32 PM EDT

[#2]

Changed both the bolt and carrier.
I'll pull the gas tube assembly to rule that out.
Thanks for the ideas.

Posted: 7/23/2017 1:24:13 PM EDT

[#3]

What brand bolt?
Is the cam pin hitting the upper receiver?

Pics of the bolt face and lugs.

Posted: 7/23/2017 2:30:41 PM EDT

[#4]

Pics of feed ramp alignment. Can indicate a barrel extension pin which is not clocked properly.

Posted: 7/23/2017 4:27:28 PM EDT

[#5]

Insufficient headspace is a possibility.........what ammo are you using and what brand barrel?

Posted: 7/23/2017 5:15:20 PM EDT

[#6]

Topic Moved

Posted: 7/24/2017 12:54:28 AM EDT

[#7]

Inspect the barrel extension lugs to make sure the are centered inside of the upper receiver, and not canted off slightly. Also try installing just the bolt carrier (No bolt, cam pin or firing pin) into the upper receiver, and see if it freely slides back/forth inside the upper receiver with no resistance.

CY6
Greg Sullivan "Sully"
SLR15 Rifles
TheDefensiveEdge.com
(763) 712-0123

Posted: 7/25/2017 5:51:05 PM EDT

[#8]

Quote History

Quoted:
Insufficient headspace is a possibility.........what ammo are you using and what brand barrel?

View Quote

I imagine this is the problem. The worn bolt had plenty of clearance, the new one's headspace is too tight for your ammo.

Posted: 7/26/2017 12:30:52 AM EDT

[#9]

You say that the action locks up when fired or when a dummy round is chambered...

Does the action lock up if the bolt is closed on an empty chamber?

The dummy round that you tried. Did you make it from a fired round or did you use a commercial made dummy round (plastic or metal)? Did you full length resize the casing before inserting the bullet. A round fired from a different gun has expanded to fill the chamber of the gun it was fired in (which is not the same size as your gun). Odds are that if a casing is not resized, it will jam when inserted into a different gun.

Posted: 8/20/2017 11:55:27 PM EDT

[#10]

A similar problem was a small piece of brass on the forward side of the locking lug. Younger eyes and a pick solved the problem.

Posted: 8/22/2017 6:52:43 PM EDT

[#11]

Provide picture of the feed ramp could be that the index of the extension is shifted and torqued.

[ARCHIVED THREAD] - Bolt locks shut and won't cycle

AR-15 » Troubleshooting

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