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AR15 bolt wont lock back


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#1 ARRH86

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Posted 18 December 2004 - 09:52 PM

I built a rifle from Model 1 Sales but it seems to have a problem.

When I put an empty mag in, I have tried several different ones, and pull the charging handle back, and let it fly, the bolt won't catch prior to the magazine. The bolt moves through its entire range of motion all the way back up.

Isn't the bolt supposed to lock back on an empty magazine?

What should I do, try more magazines? Fix it some other way?

I have no clue what I'm doing but other than it it passes all the tests I read the rifle was supposed to do.

Thanks,

Tom
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#2 Thed Re: AR15 bolt wont lock back

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Posted 18 December 2004 - 11:09 PM

Could be a few things. I have built three rifles from Model "1" Kits.

How well did the spring fit into the drilled hole for the bolt catch? Did it fit in snug, or just drop in? On two of my builds on Rock rRiver Arms Receivers I had to use a drill bit to slightly open up the hole for the spring. I am not talking about much, but the spring and plunger did not drop in very well on either. I think it was Teflon or anodize material build up causing the problem.

The stamped pice that is the bolt catch: Does it rotate/pivot freely? Any friction? If so, it may be work while to polish the edges of the bolt catch with some 600 grit paper. The oil. This must move freely up and down.

I think you already looked at the magazines. I have similar problems with some of my Orlite magazines which have been used alot. Same thing with steel aftermarket magazine with non-USGI followers.

Last of all, is the plunger installed underneath the bolt stop between it and the spring? Its a parts kit assembly mistake some overlook.

Thats what comes to mind, hope it helps ok>

-Thed
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#3 Pacman Re: AR15 bolt wont lock back

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Posted 19 December 2004 - 11:11 AM

I built a rifle from Model 1 Sales but it seems to have a problem.

When I put an empty mag in, I have tried several different ones, and pull the charging handle back, and let it fly, the bolt won't catch prior to the magazine.  The bolt moves through its entire range of motion all the way back up.

Isn't the bolt supposed to lock back on an empty magazine?

What should I do, try more magazines?  Fix it some other way?

I have no clue what I'm doing but other than it it passes all the tests I read the rifle was supposed to do.

Thanks,

Tom

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Can you push in on the bottom of the bolt release and have it hold the bolt open? If it takes any effort at all the push it in then the magazine spring may not be strong enough to push up on the bolt hold open.

Chris
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#4 ARRH86 Re: AR15 bolt wont lock back

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Posted 19 December 2004 - 04:17 PM

Ok i did the simpler pacman test first.

Yes I can push the bottom of the bolt release in and it will hold the bolt back.

I don't know how to describe how much force it took to push it in... not a lot, but some effort.

I will try to do the Thed tests later today.

I tried some more magazines and a different rifle (not mine) is doing the same thing. The other rifle does it on all magazines except one, and mine does it on all of them.
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#5 Pacman Re: AR15 bolt wont lock back

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Posted 19 December 2004 - 09:20 PM

Ok i did the simpler pacman test first.

Yes I can push the bottom of the bolt release in and it will hold the bolt back.

I don't know how to describe how much force it took to push it in... not a lot, but some effort.

I will try to do the Thed tests later today.

I tried some more magazines and a different rifle (not mine) is doing the same thing.  The other rifle does it on all magazines except one, and mine does it on all of them.

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Open the two halves and slip a magazine in and lock it. The follower should raise the tip of the bolt hold open lever. If it doesn't try and help it. If you can apply pressure and help it you may have to free up the hold open lever. If the follower doesn't make contact you may have to replace the lever. Or you may have to replace the followers with new ones.

Chris
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#6 ARRH86 Re: AR15 bolt wont lock back

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Posted 19 December 2004 - 11:32 PM

THANK YOU BOTH!

Ok, I can apply pressure and help it, and doing it this latest time it took quite a bit of pressure to help.

I can easily tell now that the bolt hold level has a lot of friction, so I need to free it up.

How do I go about doing this?

Will I need to order another pin?

And what method to grind that level down? Sandpaper or file or what?

Thanks so much for the help.

-Tom



edit: Ok I checked back over Theds post and now I see how to file it down a little. Do I need to order any replacement parts however, I don't think those pins can come out and go in again or is there something I'm not thinking about?

Edited by ARRH86, 19 December 2004 - 11:34 PM.

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#7 emclean Re: AR15 bolt wont lock back

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Posted 20 December 2004 - 09:19 AM

it is a roll pin, you will need a punch to get it out
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#8 Pacman Re: AR15 bolt wont lock back

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Posted 20 December 2004 - 11:14 AM

THANK YOU BOTH!

Ok, I can apply pressure and help it, and doing it this latest time it took quite a bit of pressure to help.

I can easily tell now that the bolt hold level has a lot of friction, so I need to free it up.

How do I go about doing this?

Will I need to order another pin?

And what method to grind that level down? Sandpaper or file or what?

Thanks so much for the help.

-Tom
edit:  Ok I checked back over Theds post and now I see how to file it down a little.  Do I need to order any replacement parts however, I don't think those pins can come out and go in again or is there something I'm not thinking about?

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I don't know if the pin is reusable but you can try it. The worst that will happen is that it will fit in the holes too loose and you take it out and replace it.

As for what part to work over with the sand paper, etc. You need to find out where it is binding. It could either be where the hold open lever pivots between the two "ears" on the lower or the little round spring detent behind the hold open lever is binding in the hole it rides in.

Are you sure you used the right spring and detent behind the hold open lever? The spring looks alot like the spring that goes in the trigger that presses up on the disconnector. The spring that goes in the trigger is tapered where the spring that goes under the hold open lever is not tapered.

Also the detent plunger thingy (that's the proper techinical term :D ) has a round tip riding against the hold open lever and should move freely in its hole.

If the spring and/or the detent plunger thingy are binding up I think it was Thed that suggested to open the hole some with a properly sized drill bit using just your fingers to move the bit. Just take some finish off inside the hole.

If the hold open lever is binding where it rides between the "ears" on the lower, I would use a small fine file and definitely mask the area with tape first. You probably just need to take some finish off here.

When you are done and you have the two halves seperated it should take no pressure at all to raise the hold open lever. It should move freely. The spring under it is about the same that a ball point clicky pen uses. This should tell you how much pressure it takes for the hold open lever to come up and hold the bolt back.

Hope this helps.

Chris
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#9 ARRH86 Re: AR15 bolt wont lock back

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Posted 20 December 2004 - 02:53 PM

Yeah I remember specifically reading about those springs being similar, so I know I put the right one in. I'm fairly certain it is where the level rides between the two receiver ears that it is binding.

I am going to take it out (try and take it out) today and see what I can do. I'll post back here how it works out and what I eventually did (Or if I get stuck and need help which is more likely).

Thanks again.
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#10 ARRH86 Re: AR15 bolt wont lock back

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Posted 20 December 2004 - 05:53 PM

Ok, I have it all apart and have sanded a bit off on the bolt hold lever.

It seems to move fairly smooth now but I have a question before I put it back together again.

How much contact is there supposed to be between the back of the trigger and the bolt hold lever? I thought about it and It seems that it shouldnt matter but now I am wondering.

I think I will be able to re-use the pin but I don't think it could go through this process again so I want to make sure I do this right the first time, so I wont have to order another one.
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#11 Pacman Re: AR15 bolt wont lock back

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Posted 20 December 2004 - 06:06 PM

Ok, I have it all apart and have sanded a bit off on the bolt hold lever.

It seems to move fairly smooth now but I have a question before I put it back together again.

How much contact is there supposed to be between the back of the trigger and the bolt hold lever?  I thought about it and It seems that it shouldnt matter but now I am wondering.

I think I will be able to re-use the pin but I don't think it could go through this process again so I want to make sure I do this right the first time, so I wont have to order another one.

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I'm sorry but I don't understand what you mean by how much contact between the back of the trigger and the bolt hold open lever. These two parts don't touch.

Chris
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#12 Pacman Re: AR15 bolt wont lock back

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Posted 20 December 2004 - 06:22 PM

I'm sorry but I don't understand what you mean by how much contact between the back of the trigger and the bolt hold open lever. These two parts don't touch.

Chris

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I just realized you probably meant the back of the magazine and the bolt hold open. I would have to look but I think from memory it is only about a 1/16 of an inch. Basically enough so that moving the mag around in the well doesn't pull the follower out from under the tip of the lever.

Chris
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#13 ARRH86 Re: AR15 bolt wont lock back

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Posted 20 December 2004 - 06:32 PM

Yeah that is what I have but I did mean the trigger mechanism and the bolt hold lever.

I know when you pull the charging handle the trigger is pulled back and won't touch the bolt hold lever, so it shouldn't matter, but on my rifle the trigger doesn't go straight vertical with where the bolt hold lever or the bolt hold lever.

I mean the trigger rubs on the bolt hold lever, it kind of leans into the lever instead of just standing up next to it.

Yeah, I'm not good. I don't think it matters at all and I'm not good at describing it but I just wanted to make sure.
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#14 Pacman Re: AR15 bolt wont lock back

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Posted 20 December 2004 - 06:39 PM

Yeah that is what I have but I did mean the trigger mechanism and the bolt hold lever.

I know when you pull the charging handle the trigger is pulled back and won't touch the bolt hold lever, so it shouldn't matter, but on my rifle the trigger doesn't go straight vertical with where the bolt hold lever or the bolt hold lever.

I mean the trigger rubs on the bolt hold lever, it kind of leans into the lever instead of just standing up next to it.

Yeah, I'm not good.  I don't think it matters at all and I'm not good at describing it but I just wanted to make sure.

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I see, you mean the hammer touches the bolt hold open lever. That is normal. In fact DO NOT release the hammer without the bolt and pin installed and DO NOT release the hammer without the upper installed. You can and probably will break the hold open lever when the hammer hits it.

Chris
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#15 ARRH86 Re: AR15 bolt wont lock back

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Posted 20 December 2004 - 07:29 PM

Alright it's all back together now and working fine.

Just needed to sand down a tiny bit on the lever itself.

Thanks for the help Pacmand and Thed.
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#16 Pacman Re: AR15 bolt wont lock back

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Posted 20 December 2004 - 10:31 PM

Alright it's all back together now and working fine.

Just needed to sand down a tiny bit on the lever itself.

Thanks for the help Pacmand and Thed.

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No problem. Glad I could finally help someone.

Chris
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#17 machineguneddie Re: AR15 bolt wont lock back

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Posted 20 December 2004 - 11:35 PM

ok....... now where are the pics.
congrats by the way
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#18 ARRH86 Re: AR15 bolt wont lock back

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Posted 30 December 2004 - 07:16 PM

Thanks!

I don't have a digital camera really at the time.

I'll see what I can do though, but it might take a while.
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