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Posted: 1/30/2006 9:28:35 AM EDT
[Last Edit: 1/30/2006 12:40:26 PM EDT by johndel]
I installed a new magpul stock on my bushmaster. Fits great works great. One problem. After a couple rounds the buffer spring pushes past the buffer retaining pin and causes the spring and retaining pin to jam up in the trigger.

I am assuming that there is too much pressure against the retaining pin. Can this be resolved by shortening the buffer spring?

Thanks for the Help
Link Posted: 1/30/2006 10:46:13 AM EDT
Is the retaining pin adjusted to the proper level/ height?

Link Posted: 1/30/2006 10:47:19 AM EDT
[Last Edit: 1/30/2006 10:49:44 AM EDT by eklikwhoa]
how would that be possible?


the bolt carrier would limit how far it would go forward.



but if you are doing this with the upper removed then it sounds believable.
did you thread the buffer tube too far?
did you damage the retaining pin?
position the buffer so that the round edge is against the retaining pin?
does the retaining pin have spring pressure forcing it upwards?
do you have the buffer tube/reciever extension lip holding the retaining pin down?

have pics?
Link Posted: 1/30/2006 10:48:32 AM EDT
Link Posted: 1/30/2006 11:11:58 AM EDT
[Last Edit: 1/30/2006 11:12:37 AM EDT by terrydavis]

Originally Posted By BravoCompanyUSA:
The buffer tube (receiver extention) is not installed forward enough.



Sometimes, the tube doesn't fit just right. It might be too far forward and unscrewing it one turn puts it too far back to hold the buffer retaining pin. If this is the case, just take a file and remove some metal so it fits. Remember to deburr the inside lip if you do this.
Link Posted: 1/30/2006 11:16:56 AM EDT

Originally Posted By VT4meGunCtrlisAntiUS:
Is the retaining pin adjusted to the proper level/ height?




yes. it looks perfect.

I installed with the upper removed.
Retaining pin is trashed. ( I think the buffer spring is pushing too hard on it)
Yes the lip is holding the pin down.

The buffer tube is installed with an .80 shim.
Link Posted: 1/30/2006 11:17:48 AM EDT
[Last Edit: 1/30/2006 11:18:10 AM EDT by johndel]

Originally Posted By terrydavis:

Originally Posted By BravoCompanyUSA:
The buffer tube (receiver extention) is not installed forward enough.



Sometimes, the tube doesn't fit just right. It might be too far forward and unscrewing it one turn puts it too far back to hold the buffer retaining pin. If this is the case, just take a file and remove some metal so it fits. Remember to deburr the inside lip if you do this.



I think i can maybe unscrew the magpul a little bit. But then I would have to install another shim right?

I'll post some pics when I get home.
Link Posted: 1/30/2006 11:28:20 AM EDT
[Last Edit: 1/30/2006 11:38:39 AM EDT by Triple_D]

Originally Posted By johndel:
Retaining pin is trashed. ( I think the buffer spring is pushing too hard on it)



The buffer should not contact the retaining pin at all, when the upper is mounted on the lower. The buffer is held off of the retaining pin by the back of the bolt carrier. The buffer only makes contact with the retaining pin when the upper is removed from the lower. All the retaining pin does is hold the buffer in the tube, when the upper is removed. If your buffer hits the retaining pin when the rifle is fully assembled, then something is very wrong. It is hard to imagine that the buffer spring is strong enough to do damage to the retaining pin, unless the buffer is slamming foward against the pin.



edit: spelling
Link Posted: 1/30/2006 11:39:05 AM EDT
I will post pics when I get home from work.

What you said is correct. When the upper is off the lower. The buffer sits on the pin.

What's happening. Is when I go shooting. After a couple shots. The gun seizes up. And when I remove the upper. The buffer spring is pushed beyond the buffer pin.

This is a very confusing topic. Hopefully I can help with the pics.

Thanks Guys.
Link Posted: 1/30/2006 11:45:14 AM EDT

Originally Posted By johndel:
I will post pics when I get home from work.

What you said is correct. When the upper is off the lower. The buffer sits on the pin.

What's happening. Is when I go shooting. After a couple shots. The gun seizes up. And when I remove the upper. The buffer spring is pushed beyond the buffer pin.

This is a very confusing topic. Hopefully I can help with the pics.

Thanks Guys.




your buffer is pushed beyond the retaining pin cause the retaining pin isnt holding the buffer.

with the upper installed it should work fine with no problems unless the small parts are coming out and jamming the trigger. the rifle will fire like normal without the retaining pin as long as you get the upper closed on the lower with the buffer in place.

do not file the magpul buffer tube! there are shims to correct the the spacing of it and should be used.
Link Posted: 1/30/2006 12:43:01 PM EDT
I had to install a smaller shim for the stock. The tube was not covering the lip of the pin. Once I screwed in a smaller shim and screwed the stock in more. It was just enough to cover the pin to keep it in position.


Thanks for all the help guys. Much appreciated.
Link Posted: 1/30/2006 12:47:25 PM EDT
so the buffer tube was not completely holding the buffer retaining pin?
Link Posted: 1/30/2006 12:50:57 PM EDT

Originally Posted By eklikwhoa:
so the buffer tube was not completely holding the buffer retaining pin?



Yes sir. You are correct. I thought that the pressure from the buffer spring was what held the buffer pin in. I was sure wrong.
Link Posted: 1/30/2006 12:58:53 PM EDT
thats what i figured you did.


there are tacked thread in the build it yourself forum which has step by step instructions and pictures to aid you in this stuff. think there is a stock one.


glad to hear its all good now.
Link Posted: 1/31/2006 3:28:47 AM EDT
Wow. I guess I should start visiting the build it yourself forum. I don't think I have ever been there. Thanks again for the help.
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