AR 15 "stuck" bolt assy

[jarheadteacher]

Hello,

Built my AR and it shoots straight and I love it. Has a problem ejecting rounds while trying to chamber a new round and I am getting a new extractor and spring soon but I have one major headache I was hoping you all might help me with.

If I pivot the upper from the lower to load my magazine, after I shut and secure the upper again, it is impossible to pull the bolt back more than a 1/4". I must use the forward assist to force it back home and remove the magazine, pivot open and shut the upper, reinstall the magazine, and then everything is just perfect !?

Anyone recommend a fix for this?

Thanks,
J

[Technical Ted]

Do you have a collapsible stock? Check that the top of the receiver end plate is flush with the top of the lower receiver so that the receiver end plate is not impeding the rearward draw and forward travel of the charging handle.

[jarheadteacher]

Thanks Ted, but no, I do not have a collapsible stock.

[Technical Ted]

Does the Bolt Carrier Group move relatively free in the upper when separated from the lower (discounting a light resistance while the bolt rotates into battery).

Tight gas rings on the bolt? Remove the Bolt Carrier Group, press the bolt into the carrier and give it a flick with your wrist. Bolt should extend under it's own momentum.

Gas tube centered in the interior Charging Handle channel at the top of the upper receiver?

Charging Handle straight?

Bolt Carrier Gas Key properly installed?

Inspect for wear at the rear of the Bolt Carrier?

Buffer Retainer symmetrical (Not bent) and not showing any signs of wear.

Forward Assist Pawl isn't protruding into the upper receiver?

Receiver Extension (AKA Buffer Tube) straight?

Just a few suggestions. Hopefully Randall will chime in soon.

[jarheadteacher]

Thanks for the suggestions Ted, but I think all is "ok" in regards to what you pointed out.

I did just notice something though:

I just heard something. After pivoting the upper to recreate the problem, one must remove the magazine, pivot the upper, THEN I JUST NOTICED THE BOLT RELEASE BUTTON, ON THE LEFT SIDE OF THE LOWER, 'CLICKS' BACK INTO POSITION when you pivot the upper open. Then close the upper again and all is fine.

It seems to have somethnig to do with the bolt release button????

Hope this jogs someone's memory.

[NeoWeird]

From the sounds of it you are experiencing problems when you first close the upper but once it starts to function everything works fine; correct?

From the sounds of it wear is NOT the problem, because it sounds like a bind somewhere, probably from stacking tolerances (short hand: when parts mesh together they have a small tolerances range, usually .01" total difference, and if you have two parts at their large end they may build excessive friction or pressure and restrict proper functioning). It sounds like maybe your bolt carrier is catching the top of your magazine and putting excessive force on the magazine by trying to push it out (maybe a bent magazine lip, or rolled bur on the carrier) and it causes a bind that is hard to remove by hand. This also explains why the magazine release moves as you install/remove the upper. When a magazine is slammed home it may be inserted in an angle that is more acceptable to the relationship of the carrier and magazine itself (straight up instead of pivoting) and it is forced into it's proper location and functions fine.

If that is the case, you might want to check the front of your magazine lips. As the upper pivtots down it contacts the front of the magazine first and it might be catching a slightly bent inward lip and binding. When the magazine is inserted normally the rear of the magazine touches the carrier first and it might hit the proper spot and through tension on it's walls it pushes the front of the magazine into battery. Might want to also check the corresponding locations on the bolt carrier as well.

Also, the carrier and bolt should be fully home when you take the upper off. When you say you have to force the carrier home do you mean you just have to apply pressue forward to releave the tension or do you mean it is actually out a bit when you put it back on? Either way, you may want to just push on the rear of your carrier and make sure it is locked and full home as you pivot it back down on the upper. Wouldn't hurt.

[ar15barrels]

The hammer is resting on the bolt catch.

When you finish shooting the ten rounds, the bolt catch is pushed up by the magazine follower.
At some point, you must be releasing the hammer before you open the gun, or maybe before you load the magazine.
After you load the mag, the hammer is still holding the bolt catch.

Solution:
Manually cock the hammer before closing the upper and lower together.
This lets the bolt catch drop down before you crush the bolt carrier against it.

[jarheadteacher]

NW,

Will reply to your thoughts here as I think you are the closest to the cause so far.
My replies in caps in your letter.

From the sounds of it you are experiencing problems when you first close the upper but once it starts to function everything works fine; correct? CORRECT, BUT, I MUST RELEASE THE MAGAZINE, PIVOT OPEN AND SHUT THE UPPER, AND ONLY THEN, IS EVERYTHING OK. JUST RELEASING THE MAGAZINE DOES NOT FIX IT...NOR DOES JUST OPENING AND CLOSING THE UPPER. THE MAGAZINE MUST BE RELEASED AND THEN THE UPPER PIVOTED, AND THAT IS WHEN I HEAR THE 'CLICK' ANDTHE BOLT CARRIER BUTTON MOVES AND THEN ALL IS WELL IN THE WORLD.

From the sounds of it wear is NOT the problem, because it sounds like a bind somewhere, probably from stacking tolerances (short hand: when parts mesh together they have a small tolerances range, usually .01" total difference, and if you have two parts at their large end they may build excessive friction or pressure and restrict proper functioning). AGREED It sounds like maybe your bolt carrier is catching the top of your magazine and putting excessive force on the magazine by trying to push it out THIS SEEMS POSSIBLE, YES.

(maybe a bent magazine lip, or rolled bur on the carrier) I WILL CHECK THE CARRIER. IT IS NOT THE MAGAZINES. I HAVE MANY MAGAZINES, BRAND NEW, AND HAVE BORROWED OTHERS AT THE RANGE...ALWAYS THE SAME PROBLEM. EVEN BORROWED SOME ONE'S UPPER AT THE RANGE ON MY LOWER AND HAD NO PROBLEMS. and it causes a bind that is hard to remove by hand. This also explains why the magazine release moves as you install/remove the upper. IT IS NOT THE MAGAZINE RELEASE THAT MOVES, IT IS THE BOLT RELEASE. When a magazine is slammed home it may be inserted in an angle that is more acceptable to the relationship of the carrier and magazine itself (straight up instead of pivoting) and it is forced into it's proper location and functions fine.

If that is the case, you might want to check the front of your magazine lips. As the upper pivtots down it contacts the front of the magazine first and it might be catching a slightly bent inward lip and binding. When the magazine is inserted normally the rear of the magazine touches the carrier first and it might hit the proper spot and through tension on it's walls it pushes the front of the magazine into battery. Might want to also check the corresponding locations on the bolt carrier as well. YES, TO THE BOLT CARRIER. I CAN SHARE ALSO THAT THE BOLT RELEASE BUTTON/PIECE AT THE REAR OF THE MAGAZINE WELL IS 'SHINY' IN SPOTS INDICATING TO ME WEAR

Also, the carrier and bolt should be fully home when you take the upper off. THEY ARE, I CAN NOT OPEN THE UPPER UNTIL THE FORWARD ASSIST SEATS THE CARRIER AND BOLT FULLY. When you say you have to force the carrier home do you mean you just have to apply pressue forward VIA THE FORWARD ASSIST, YES. to releave the tension or do you mean it is actually out a bit when you put it back on (NO)? Either way, you may want to just push on the rear of your carrier and make sure it is locked and full home as you pivot it back down on the upper. Wouldn't hurt.

[jarheadteacher]

Randall,

Thank you for your input but I am afraid that is not the answer. Hammer forward or cocked makes no difference. The problem remains.

[Whiterabbit]

I know this thread is from 2007 but I will reply. Not for the Original Poster, but for google search.

In a google search for AR bolt binding, this thread comes up as the top result from the calguns website. Thus, an answer here can help other folks searching for a real answer.

I had this issue. Exactly as stated. Down to the smallest detail.

This is the answer: it does not readily come up in a google search unless you nail the search terms:

http://home.comcast.net/~jesse99/AR_Carrier.html

You can tell you have the issue if you force the bolt lock down and pull the charge handle. Of course you can hold the bolt catch down hard enough to bind the bolt under any circumstance, but at some reasonable point you can make it act exactly as above.

In my case, I used a chalk paint pen as a sort of inlet black. Painted the catch and cycled the bolt in the stuck condition several times, then looked for the area where the chalk was worn, and relieved that area. Now, the bolt is incredibly slick. Surprisingly so. Of course it still locks back just fine and operates as expected.

Anyways, for future google searchers who stumble on this thread, the link above is a great resource.

No further response is needed in the general sense, the thread can go back to archive. It'll keep popping up in the google searches.

[SocomM4]

Why are you pivoting the upper when loading? Try one less round in the magg.

[ar15barrels]

Why are you pivoting the upper when loading? Try one less round in the magg.

Fixed magazines were common in 2007.

[Sonic_mike]

Why are you pivoting the upper when loading? Try one less round in the magg.

Sounds like the op was using the prince50 mag lock.