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M16 Help needed
3/11/2012 7:03:40 PM
A neighboring police Department gave me a FA DPMS 11.5 inch ar15 to work on, and I am having trouble diagnosing why it is doing what it is doing.
The problem: fires any where from 1 to 3 rounds on FA then ends in a dead trigger.
What is happening: Auto sear is not engaging the hammer. When full auto fire stops, the hammer is forward and there is a live round in the chamber.
I ran the DPMS upper on a M16 a1 lower and it works fine. I ran my 11.5 upper on the DPMS FA lower and it works fine. Cycling by hand everything works fine. Seems to be properly gassed as the bolt locks back on an empty mag. Does any one have any idea what could be causing this.
The problem: fires any where from 1 to 3 rounds on FA then ends in a dead trigger.
What is happening: Auto sear is not engaging the hammer. When full auto fire stops, the hammer is forward and there is a live round in the chamber.
I ran the DPMS upper on a M16 a1 lower and it works fine. I ran my 11.5 upper on the DPMS FA lower and it works fine. Cycling by hand everything works fine. Seems to be properly gassed as the bolt locks back on an empty mag. Does any one have any idea what could be causing this.
3/11/2012 7:22:08 PM
Originally Posted By MPD444:
A neighboring police Department gave me a FA DPMS 11.5 inch ar15 to work on, and I am having trouble diagnosing why it is doing what it is doing.
The problem: fires any where from 1 to 3 rounds on FA then ends in a dead trigger.
What is happening: Auto sear is not engaging the hammer. When full auto fire stops, the hammer is forward and there is a live round in the chamber.
I ran the DPMS upper on a M16 a1 lower and it works fine. I ran my 11.5 upper on the DPMS FA lower and it works fine. Cycling by hand everything works fine. Seems to be properly gassed as the bolt locks back on an empty mag. Does any one have any idea what could be causing this.
A neighboring police Department gave me a FA DPMS 11.5 inch ar15 to work on, and I am having trouble diagnosing why it is doing what it is doing.
The problem: fires any where from 1 to 3 rounds on FA then ends in a dead trigger.
What is happening: Auto sear is not engaging the hammer. When full auto fire stops, the hammer is forward and there is a live round in the chamber.
I ran the DPMS upper on a M16 a1 lower and it works fine. I ran my 11.5 upper on the DPMS FA lower and it works fine. Cycling by hand everything works fine. Seems to be properly gassed as the bolt locks back on an empty mag. Does any one have any idea what could be causing this.
Bolt (carrier) bounce.
Use a heavier buffer.
3/11/2012 7:47:56 PM
It came from the factory with a h2 buffer. I tried a 5.4 oz 9mm buffer with the same result.
3/11/2012 8:01:33 PM
Then try an H3 or Spike's ST-2 tungsten buffer.
Next thing to try is to do a complete spring replacement, including a new buffer spring.
Then trying different, or heavier-weight carriers.
You might have to try a new auto sear and/or hammer if the auto sear is truly not catching the hammer - though such a malfunction is nearly unheard-of in a factory machinegun receiver with GI spec parts.
Next thing to try is to do a complete spring replacement, including a new buffer spring.
Then trying different, or heavier-weight carriers.
You might have to try a new auto sear and/or hammer if the auto sear is truly not catching the hammer - though such a malfunction is nearly unheard-of in a factory machinegun receiver with GI spec parts.
3/11/2012 8:12:52 PM
Originally Posted By Circuits:
You might have to try ... GI spec parts.
You might have to try ... GI spec parts.
I remember about 6 months to a year ago a guy had DPMS full auto parts that were giving him problems as the were far off spec.
3/11/2012 8:31:23 PM
I also tried a wolff xp spring with the h2 buffer. My spikes t2 is the same weight as the h2 in it, at 4.1 oz.
3/11/2012 9:08:15 PM
Bolt bounce blues. Heavier buffers dont always solve bolt bounce problems. You need to buy stock in Enidine, or MGI. If the gun will run semi all day its most likley bounce. If you can hand cycle it(no ammo for this) in auto and hammer falls every time just between 1/8"-1/16" before carrier hits the barrel extension, its bounce problems. If you where close to NW Ohio I would love to get it running for ya.
3/11/2012 9:19:47 PM
It will run semi just fine. And the gun ran through the 1st 200 rds or so with no issue. Would bopt bounce just come on like that?
3/12/2012 12:05:10 AM
Topic Moved
3/15/2012 8:31:25 PM
Make your life easy. Just get a Vltor A5 receiver extention ,their spring and buffer. No more bolt bounce thats for sure. If you have a A2 stock and rifle buffer you could try that to. If it cures the problem . Then it was bolt bounce and you need to get the A5
BMC has them . Reading your post again you said this upper ran fine on your A1 lower. Is there an A1 stock on it ? If so thats telling you something right there.
BMC has them . Reading your post again you said this upper ran fine on your A1 lower. Is there an A1 stock on it ? If so thats telling you something right there.
3/16/2012 11:51:41 AM
There was an A1 stock on the A1 lower. I just had the department sent it back to DPMS. Its a new gun they should be able to get it to work.
3/16/2012 11:21:54 PM
Originally Posted By MPD444:
There was an A1 stock on the A1 lower. I just had the department sent it back to DPMS. Its a new gun they should be able to get it to work.
There was an A1 stock on the A1 lower. I just had the department sent it back to DPMS. Its a new gun they should be able to get it to work.
Getting it to work and having a reliable weapons system are two differant things. The A5 brings a lot to the table.
5/11/2012 4:59:37 PM
Originally Posted By Circuits:
Then try an H3 or Spike's ST-2 tungsten buffer.
Next thing to try is to do a complete spring replacement, including a new buffer spring.
Then trying different, or heavier-weight carriers.
You might have to try a new auto sear and/or hammer if the auto sear is truly not catching the hammer - though such a malfunction is nearly unheard-of in a factory machinegun receiver with GI spec parts.
Then try an H3 or Spike's ST-2 tungsten buffer.
Next thing to try is to do a complete spring replacement, including a new buffer spring.
Then trying different, or heavier-weight carriers.
You might have to try a new auto sear and/or hammer if the auto sear is truly not catching the hammer - though such a malfunction is nearly unheard-of in a factory machinegun receiver with GI spec parts.
My 11.5" Colt with original carbine buffer and spring is doing the same thing as the OP's gun. I installed an H2 buffer but with same results. What buffer spring would you recommend? What would you recommend for a heavier bolt carrier?
5/11/2012 5:21:19 PM
I personally try and stick with a standard M4 buffer recoil spring. I am not a big fan of the extra power springs as they can cause problems and speed up cyclic rate.
From a heavy buffer perspective I like the Colt B or X buffers. The X Buffer is about as heavy as you can go in a carbine form factor buffer. The bodies are made of steel and the B has 1 steel and 2 tungsten sliding weights and the X has three tungsten weights which act like a deadblow hammer.
The Colt X is almost double the weight of an H2 (4.6 vs 7.9 ounces) so you have some more opportunity to put mass behind the carrier to slow it down
Another thing to check is to make sure that you have a good/new fresh hammer spring and new gas rings as well. The hammer spring will help impart more energy to the firing pin, even if there still is a little bit of carrier bounce, and the gas rings create drag that counter act the tendency for the carrier to separate from the bolt.
You can check your gas rings via a simple test, pull the bcg out of the gun and set the carrier ass-end up on a bench with the bolt face pointing straight down. A gun with fresh gas rings should easily be able to stand with the bolt and carrier in the extended position and should take some pressure to collapse. If the carrier is able to just collapse on the bolt of takes almost no pressure to push down, you need to replace the rings.
I would start with a new hammer spring and a fresh set of gas rings as that is a sub $25 investment. If you have a recoil spring of unknown origin that replace it with a factory fresh colt M4 bufrer tube spring.
From a heavy buffer perspective I like the Colt B or X buffers. The X Buffer is about as heavy as you can go in a carbine form factor buffer. The bodies are made of steel and the B has 1 steel and 2 tungsten sliding weights and the X has three tungsten weights which act like a deadblow hammer.
The Colt X is almost double the weight of an H2 (4.6 vs 7.9 ounces) so you have some more opportunity to put mass behind the carrier to slow it down
Another thing to check is to make sure that you have a good/new fresh hammer spring and new gas rings as well. The hammer spring will help impart more energy to the firing pin, even if there still is a little bit of carrier bounce, and the gas rings create drag that counter act the tendency for the carrier to separate from the bolt.
You can check your gas rings via a simple test, pull the bcg out of the gun and set the carrier ass-end up on a bench with the bolt face pointing straight down. A gun with fresh gas rings should easily be able to stand with the bolt and carrier in the extended position and should take some pressure to collapse. If the carrier is able to just collapse on the bolt of takes almost no pressure to push down, you need to replace the rings.
I would start with a new hammer spring and a fresh set of gas rings as that is a sub $25 investment. If you have a recoil spring of unknown origin that replace it with a factory fresh colt M4 bufrer tube spring.
