M16 SBR Problems

[deadly0311]

To those of you who are pretty well versed in short barreled full autos here is my problem. I have an M16 lower with Safe/Semi/Full trigger pack. I have a 10.5" barrel w/ carbine length gas system. I cannot get it to reliably run, sometimes it will run fine for about 10-12 rounds before a double feed, sometimes it wont go 2 rounds before a double feed. It occurs on Auto and Semi, I have used about 15 different magazines, regular- H3 buffers. I for the life of me cannot figure out why it will not run right.

Any help would be greatly appreciated.

 

[Turk]

Re: M16 SBR Problems

Gas port.

 

[deadly0311]

Re: M16 SBR Problems

Need to be enlarged or restricted?

 

[Mattrmvpd]

Re: M16 SBR Problems

ENLARGE most likely. I run a 10" and once it was opened up it feeds and eats more than i can buy.

Matt (LEO SOUTH GA.)

 

[Turk]

Re: M16 SBR Problems

Can't remember, so long ago! Short one's are real finicky. I had the same problem on mine. I would call this guy http://www.ajbrownarms.com/
He is rumoured to know a thing or two about them!

 

[slothlacrosse]

Re: M16 SBR Problems

Check the extractor spring. Make sure it's a 3 coil spring and it has an o-ring.

 

[deadly0311]

Re: M16 SBR Problems

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Turk</div><div class="ubbcode-body">Can't remember, so long ago! Short one's are real finicky. I had the same problem on mine. I would call this guy http://www.ajbrownarms.com/
He is rumoured to know a thing or two about them!

</div></div>

Yeah I would say AJ knows a thing or two about them

 

[Turk]

Re: M16 SBR Problems

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: slothlacrosse</div><div class="ubbcode-body">Check the extractor spring. Make sure it's a 3 coil spring and it has an o-ring. </div></div>
I don't think that's the problem. Does the problem go away for 10-15 rounds after you clean it and starts again?

 

[SwatSgt]

Re: M16 SBR Problems

Same issue with our Colt's at work (11.5" barrel full auto) ours would fire 5-6 rounds sometimes and 10-12 the next but would misfeed every time they stopped functioning.


It was clogged gas ports and a semi clogged gas tube. Replaced gas tubes and had ports opened up on barrel by AR manufacture company in the city. It now runs like a champ. Did same to other rifles just to make sure they didn't malfunction later on. These rifles were about 15 years old when this happened if that helps. Tried everything else you mentioned before pulling the gas tubes and seeing the gas ports on the barrel were mostly blocked. The carbon blocking the holes was so hard we had to use a brass punch and a hammer to clean them so they could measure them. After measuring them the gun smith said they needed to be enlarged so they fixed them right up for us.

 

[deadly0311]

Re: M16 SBR Problems

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SwatSgt</div><div class="ubbcode-body">Same issue with our Colt's at work (11.5" barrel full auto) ours would fire 5-6 rounds sometimes and 10-12 the next but would misfeed every time they stopped functioning.


It was clogged gas ports and a semi clogged gas tube. Replaced gas tubes and had ports opened up on barrel by AR manufacture company in the city. It now runs like a champ. Did same to other rifles just to make sure they didn't malfunction later on. These rifles were about 15 years old when this happened if that helps. Tried everything else you mentioned before pulling the gas tubes and seeing the gas ports on the barrel were mostly blocked. The carbon blocking the holes was so hard we had to use a brass punch and a hammer to clean them so they could measure them. After measuring them the gun smith said they needed to be enlarged so they fixed them right up for us. </div></div>


Sounds about right, Ill look at having the port opened up. Turk, have wiped the bolt down and being clean or dirty makes no difference....it still persists.

 

[Turk]

Re: M16 SBR Problems

If I cleaned mine thoroughly; it would reappear after about 10 rnds.

 

[KYS]

Re: M16 SBR Problems

1. Gas Port is to small
2. Check extractor spring
3. Hydraulic buffer while a bit pricey, has helped every full auto run that I have encountered with problems. A local manufacturer does sell them and install them. His 10.5" FA's run like a top.

Also, make sure you are properly greased. Frog Lube is what we use here. Follow its directions and you will be fine for many firings.

 

[JaneDoe]

Re: M16 SBR Problems

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: KYS338</div><div class="ubbcode-body">1. Gas Port is to small
2. Check extractor spring
3. Hydraulic buffer while a bit pricey, has helped every full auto run that I have encountered with problems. A local manufacturer does sell them and install them. His 10.5" FA's run like a top.

Also, make sure you are properly greased. Frog Lube is what we use here. Follow its directions and you will be fine for many firings. </div></div>

I had a registered receiver M16 with a factory LMT 10.5" upper that gave me similar problems, so I tried these things too.

I went through all the buffers I could find at the time - standard, H2, AAC Cyclic Rate Reducer - as well as slowly opening the gas port. I changed extractors. I changed bolts - LMT enhanced to standard M16. I could never get it to be 100% reliable.

I ended up putting a 11.5" barrel with standard M16 bolt and it worked flawlessly with a H2 buffer and the gas port as it came from the factory. The upper still continues to run 100% as a semi-auto SBR.

 

[jrhtx]

Re: M16 SBR Problems

10.5" are hard to trouble shoot.
You haven't said if the barrel is Colt or?? Do you know if the chamber is cut for 556, 223, or Widley(sp?)?
For 5.56mm
Colt's gas port sizes are:
* 10.5" - .093
* 11.5" - .081
* 14.5" - .063
* 16" - .063
Check that your extractor spring and rubber is the latest upgrade, I think it is black. Also install an o-ring or defender under the extractor.
The chamber could be rough if it is not chrome or it could be tight.
Try loading 10-15 mags with 1 round. Fire them as fast as you can load the mags. Does the round extract completely? Mag lock the bolt back? If the bolt is not locking back on each single shot, gas problem.
You also might have to look at the DPMS 2 piece buffer like the 9MM buffer. Helps with bolt bounce.

 

[slothlacrosse]

Re: M16 SBR Problems

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Turk</div><div class="ubbcode-body">
I don't think that's the problem. Does the problem go away for 10-15 rounds after you clean it and starts again? </div></div>

Sounds exactly like what happened with my SBR and I did the buffer/spring/gas port, but still had the problem.

Finally, someone mentioned the o-ring (which was sitting in a plastic bag on my gun bench).

Just thought I'd throw it out there.

 

[deadly0311]

Re: M16 SBR Problems

Opened the gas port, installed a new extractor spring and o-ring, with H2 buffer and it runs like a top

 

[SwatSgt]

Re: M16 SBR Problems

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Deadly0311</div><div class="ubbcode-body">Opened the gas port, installed a new extractor spring and o-ring, with H2 buffer and it runs like a top </div></div>

Good job now go spray $6-8 bucks out the barrel....

Glad you got it figured out have fun

 

[bm11]

Re: M16 SBR Problems

Good thread, bought a 10.5" switchblock upper for my 16 which will be clearing eventually so this thread may come in handy!