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Page AR-15 » Troubleshooting
AR Sponsor: bravocompany
Posted: 4/23/2003 1:42:50 PM EDT
I have reassembled my 16" CAR preban.  When I test fired it, it chambers and fires, ejects and chambers the next round just fine.  Except that it doesn't cock the hammer.  The lower parts are from an assortment of AR-15 parts I have collected  over the years and appear to be new.

The hammer cocks fine when tested manually.

What gives?

Link Posted: 4/23/2003 5:44:42 PM EDT
Sorry to hear of your problems. Let's get some more info out here so we can be of more help.

Does your rifle have a light trigger pull? Very little creep? If so the sear ledge may not be large enough to safely retain the hammer after firing.

Are the springs strong on the trigger and hammer?

Have there been any double-fires?

With the lower separated, try cocking the hammer by hand. Now grab it from above and lift, to try to get it to fall w/o pulling the trigger, aka pushoff.

If the hammer can be pried up and made to drop, then the sear engagement angle has been altered and the hammer is following the carrier down. Replace the hammer or FCG if this is the case.

When you release the trigger from the rearward (fire) position to allow it to reset, does the reset take place near the end of the trigger pull (soon after it begins going fwd) or near the end of the trip back to resting position? This will give clues as to the state of this rifle's disconnector timing.

Chances are, your trigger is out of spec. Could be the hammer itself, but I'm putting my green on the trigger nose being out of spec, coupled with a disconnector that needs adjusted to function better in this weapon.

Good luck; hope this helps...
Link Posted: 4/23/2003 6:14:33 PM EDT
If it used to work and now doesnt after you "re-assembled" it...

Check to make sure your disconector spring is installed with the wide end down.

Otherwise, I suspect your disconector is not properly engaging the hammer.  Replace the disconector first, it's cheaper.

Link Posted: 4/24/2003 1:26:47 AM EDT
Thanks for the info guys.  When I was manually working the action I didn't notice anything funny but then again I wasn't looking for specifics.  I have another couple of hammers and triggers so I will test the current one and swap them out.

I believe the springs are new.

This is not the original trigger group which came with the rifle.  It was assembled in 1982 and had M16 parts (except for the sear) which I have gotten rid of since.  I should have just ground the offending bits off that trigger group instead, but I after discovering I didn't have AR-15 parts in there I just got rid of them.

Thanks guys, I'll let ya know what I find.

Link Posted: 4/24/2003 2:53:11 PM EDT
Here goes...

It definitely has trigger creep.

It doesn't double fire.

I'm not sure what you mean by reset on the trigger.

I'll try and replace the springs with some off a blister carded set.

I tried to move the hammer off the trigger nose and it doesn't budge.

The spring under the disconnector is installed correctly, big side down.

When I compare the trigger to the other two I have, the others have two spring holes!  The one I'm using has only one.

The disconnector appears to have been machined whereas the others I have are obviously stamped.  The stamped ones show a flat side and a rounded edge on the other.  The one I'm using is machined and is thicker than the stamped ones.  Otherwise they are pretty much the same but not quite.

The hammers look the same except for a rectangle on the face (where it would strike the firing pin). I'm using the one without the raised rectangle.

Maybe part of the problem is that I don't even remember where I got these parts...I have just collected them over the years since I orginally got my rifle (1982).  Perhaps I should buy a new set?


Link Posted: 4/24/2003 3:20:25 PM EDT

It sounds like your hammer is not being retained during the cocking stroke by the disconnector.

With the rifle unloaded.

Pull and hold the trigger back, then pull all the way back on the charging handle and let it fly forward. Release the trigger and pull it again. The hammer should be retain when the carrier slams home, then released once you have released the trigger and re-pulled it.

Now charge the weapon again with the trigger held back, then very, very slowly release the trigger (do this several times). The hammer should be released by the disconnector, and then retained by the trigger sear. If the hammer slips and fires during either test, then either you are using a small FCG in a large pin hole receiver, or the disconnector needs to be adjusted (.040 removed from the front foot of the disconnector where it rides on the front of the trigger.

P.S. Learn the difference between a semi AR-15 fire control group and a M-16 group.  The two spring trigger is a M-16A2 trigger used for the burst kit (uses a burst disconnector and a semi disconnector with a tail to allow the M-16a2 selector to disengage the semi disconnector..
Link Posted: 4/25/2003 12:24:31 AM EDT

I tried both those tests and it passed.  I do remember earlier in the evening I was testing the disconnector by holding the trigger all the way back with my thumb, then pulling the trigger and holding it in the fire position all while letting the hammer to see if it caught it.  The first couple of times the FCG was slow to let the hammer go forward, but then it loosened up and caught the trigger.  It was almost as if the action was sluggish.  I did thoroughly oil it before this point.

I did notice that with my 20" AR the action has polished surfaces on both the trigger and hammer, while these others don't.

I will have to go back across the street this afternoon and retest it with live fire.

Can I use the M-16 trigger without getting into trouble?  If not, is it legal for me to sell it or trade it for AR-15 parts?

Link Posted: 4/25/2003 1:05:54 PM EDT
One of the things that I do on the disconnector before I install it, is I take a steel counter sink and clean up the trigger pin entry on both sides (slight bevel).  This prevents the disconnector from binding up on the trigger slot or the pin due to any drilling burs.

It sounds like your disconnector had a bur and wore off.

As for M-16 parts in an AR-15, the last time I said anything about the subject, I got my head tore off (flamed big time).  I will just say that if you have an AR-15, use semi ar-15 parts.
Link Posted: 4/26/2003 12:12:02 AM EDT
Thanks Dano523.

I couldn't test fire it due to the weather, maybe today.

I have sort of gotten the idea from various sources that M-16 parts in an AR-16 were a no-no.  Even though I don't own an auto sear, I'm hesitant to use them.  There's a gun show this weekend and I may try to trade the triggers in on some AR types.

Link Posted: 4/27/2003 4:19:31 AM EDT
carefull trying to trade '16 parts for '15 parts... sommeone is likely to think you are with F-troop.
Link Posted: 4/27/2003 2:31:57 PM EDT
>>>sommeone is likely to think you are with F-troop. <<<

Yup, that occured to me.  I wound up just grounding off the M-16 bits off the trigger and disconnector with my dremel tool.  I threw the trigger in the trash.

Sad to have to throw away perfectly good parts like that, but the current atmosphere is "guilty first, innocent never" I suppose.

I have ordered a new set of parts from Bushmaster, that ought to fix things.

Link Posted: 5/6/2003 5:21:46 AM EDT
Just a chance, is your buffer retainer in correctly? This happened to me when it wasn't installed correctly the bolt wouldn't cock the hammer. just a thought.
Link Posted: 5/7/2003 3:29:27 PM EDT

I sort of tested that...it seems to be in correctly.  I wound up replacing the entire FCG as it turned out the trigger was rough on the inside where the pin went, plus it didn't have the J pin.  After about ten rounds, the pin fell out of one side and the rifle failed to fire.

But it's all better now.


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