Need help troubleshooting m16

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[ARCHIVED THREAD] - Need help troubleshooting m16

Posted: 8/13/2016 1:30:37 AM EDT

I need some help troubleshooting a m16. It's a late sixties colt a1 semi and full auto. What it's doing is it will work fine in semi auto mode but when switched to full auto it will fire one round it will feed a new shell into the chamber but it appears that the hammer is following the bolt down. Like the auto sear isn't catching the hammer. I tried a different upper on it with same results. I was told that it was working with the stock 20" upper and a1 fixed stock. The owner changed the stock to a magpul stock. Thanks

Posted: 8/13/2016 1:52:26 AM EDT

[#1]

Was it changed to a collapsible buffer tube and stock? Google m16 bolt bounce, may have the wrong buffer or an el cheap chinese buffer. Hand cycle it without ammo in f/a, holding the trigger down as you let the bolt run forward and see if the sear is catching and releasing at slow speed.

Posted: 8/13/2016 2:50:09 AM EDT

[#2]

yes it was changed to a collapsible stock I looked at the buffer and it does look like a cheap piece of junk. Which buffer should a full auto collapsible stock have?

Posted: 8/13/2016 4:28:23 AM EDT

[#3]

Maybe an h2, you should be able to rattle it and hear the tungsten weights, plenty of good brands out there. What length barrel? I've never had a problem with an h2 in any of my lower with my lightning link.

Posted: 8/13/2016 9:17:11 AM EDT

[#4]

You may get more answers by posting (or asking the Moderator to move) your question in the M16 specific Forum two Forums below here. In any case, I have never had any problems using a "9 mm" buffer when shooting 5.56, 9 mm, or .45 ACP ammo of good quality.

Best of luck resolving your issue; and enjoy one of the finest automatic firearms that there is.

Posted: 8/13/2016 10:06:46 AM EDT

[#5]

Sounds like bolt bounce. H2 buffer should correct the issue. What are the full specs on the rifle - upper/barrel/bolt group, is the fire control group factory Colt, whose carbine receiver extension? At a minimum I suggest buying a H2 buffer (and a true H2, not some aftermarket Spikes or other that uses something other than counter weights inside the buffer). But I would also buy a new carbine action spring.

Posted: 8/13/2016 11:59:23 AM EDT

[#6]

Might want to also check
your auto sear timing as well to make sure the sear isn't releasing the hammer
to early:

Copied from: http://www.quarterbore.com/nfa/dias.html

Remove any magazine and ammo
from the gun.
<o:p></o:p>

Set the selector on the full
auto position.
<o:p></o:p>

Drop the hammer with the
trigger (you did check to see the chamber was empty right?)
<o:p></o:p>

Now you need your timing gages
( The cheapest is drill shanks at the required dimensions. I use three,
one early timing gage .12 dia, one correctly timed gage .10 dia, and one
late timed gage .08 dia.)
<o:p></o:p>

Secure the trigger in the fired
condition (rearward) with wire. Using the charging handle pull the bolt
carrier all the way to the rear but do not let it go, slowly lower the
carrier towards the front until you have a 1/2" gap left between the
carrier and barrel extension.
<o:p></o:p>

Insert the early timed gage in
between the colt carrier and the barrel extension (not the bolt head) and
slowly lower the bolt carrier with the charging handle. If the auto sear
releases then your gun is out of time (early) and will most likely give
you light primer hits. If not go to step 7.
<o:p></o:p>

Slightly retract the charging handle
and remove the early gage and insert the late gage. Slowly lower the
carrier until the carrier rest on the gage that is between the bolt
carrier and the barrel extension. The hammer should have dropped, if it
did not the gun is out of time (late) and will most likely either not
release the hammer or act sluggish and have a slow cyclic rate. If it
dropped go to step 8.
<o:p></o:p>

Pull back on the charging
handle and recock the gun while removing the late gage. slowly lower the
bolt carrier with the "go" or correctly timed gage until the
bolt carrier rest on the gage that is against the barrel extension. The
hammer might release or might not.
<o:p></o:p>

The key is to set the timing
so the hammer falls with the 0.10 diameter gage but not the early gage.
Assuming that the hammer was released on this gage but not the early gage the
gun is timed.
<o:p></o:p>

Posted: 8/13/2016 5:53:27 PM EDT

[#7]

Could be a timing issue with the sear and BCG, not releasing the hammer at the correct time. You do have a m16 BCG in it right? an ar15 BCG will work fine in semi but when switched to auto it will fire one round and stop.

Posted: 8/13/2016 7:31:28 PM EDT

[#8]

Is the primer dimpled at all on the round that doesn't fire?

If so then it's bolt bounce. Stock to a H2 or H3 buffer and you should be good to go.

Posted: 8/17/2016 5:33:07 PM EDT

[#9]

Sounds like it's going to be bolt bounce . I have a heavier buffer on order ill keeps everyone posted if that works

Posted: 8/17/2016 9:24:34 PM EDT

[#10]

Just sell me the gun for $5,000 and I'll just deal with the issue myself. No point in you being miserable...

Posted: 8/18/2016 12:05:55 PM EDT

[#11]

Topic Moved

Posted: 8/18/2016 1:29:06 PM EDT

[#12]

It is bolt bounce, some one may have changed the buffer over the years and put the incorrect one in it. Pick up a true H2 buffer and it should fix the problem.

Posted: 8/18/2016 6:48:18 PM EDT

[#13]

I had the same problem. Over gassed 12" upper, nice I out an H3 problem gone and ROF dropped dramatically.

Posted: 9/3/2016 4:52:01 PM EDT

[#14]

Edit- wrong thread.

Posted: 9/11/2016 7:32:38 PM EDT

[#15]

Any update OP?

[ARCHIVED THREAD] - Need help troubleshooting m16

Armory » M-16

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