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Old February 20, 2016, 11:52 PM   #1
Machineguntony
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Help with M16 malfunction

Tonight, while shooting my M16, the bolt refused to go back into the buffer tube. I disassembled the upper and pulled out the recoil spring in the buffer tube, and a ring shaped piece of plastic fell out (see pic below). I'm thinking that the ring is a piece of the buffer. Am I correct?

One of the guys at the range said that I need an H3 buffer, as the machine gun combined with the short barrel is probably over-gassing the gun. Do you guys agree?

What buffer do you guys recommend?







This is the gun. It is a registered M16 lower, with GI auto sear, 11.5 inch Colt LE upper (not the original upper), with some silencer that I forget the brand of. The buffer is also not the original buffer. It is just the buffer that came with the collapsible stock. I run this gun in silenced full auto a lot. A very fun gun.

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Old February 21, 2016, 01:56 AM   #2
Theohazard
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I'll bet you're right, that's most likely a piece of the buffer.

I'm guessing that you're using a lightweight carbine-weight buffer because that's what comes with most buffer system/stock combo packages. A carbine buffer is way too light for your setup; the full-auto and the short barrel don't help, but the biggest thing over-gassing your gun is the silencer. Your BCG is unlocking too soon and slamming way too hard against the back of the buffer tube, and that's why the end of your buffer is all beat up. You need an H2 or an H3 buffer. Not only will a heavier buffer slow down the cyclic rate, making the gun more controllable and greatly reducing parts wear, but it will also lower the amount of gas you get in your face.

I have a similar problem with my new 10.3" LMT, for some weird reason LMT shipped it with a carbine buffer. It's already overgassed without my silencer, and way over-gassed with it. My buddy loaned me a heavier H buffer, but I didn't even bother to try it yet, I'm sure I need an H2 or H3.

Last night I was online looking to order one or the other, and I came across Griffin Armament's SOB buffer (stands for Suppressor Optimized Buffer). It's designed to handle the extra pressure that a silencer puts on a buffer system: It's supposed to cushion the blow better when the buffer hits the end of the buffer tube. I don't know if that part works or not, but what I like about it is that it weighs a little more than an H2 buffer, but not as much as an H3.

I want the heaviest buffer that will still allow my LMT to run flawlessly without the silencer, and I know that an H2 will do that. An H3 will work even better when suppressed, but I was worried it wouldn't be 100% reliable when the rifle was shot unsuppressed and really dirty. So the weight of the SOB seems perfect. It should arrive within the week and I hope to be able to test it soon after that.
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Old February 21, 2016, 08:51 AM   #3
Machineguntony
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Should I get an H2 or H3? How do I know if I should be using H2 or H3? Is there a test?
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Old February 21, 2016, 09:06 AM   #4
2damnold4this
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I'm no expert but I would get the heaviest buffer you can that will allow the bolt to lock back. For example, you can put the H2 buffer in, load one round in a magazine and if the bolt locks back after firing, try the H3. If the bolt won't back with the H3, then use the H2. With a suppressor, you may have to go to an adjustable gas block.
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Old February 21, 2016, 11:31 AM   #5
JT-AR-MG42
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MT,
In my 11.5, I use either an H2 or a 'dead blow' two piece buffer I picked up at a show.
Seems smooth with my loads and the H2, and a pal wants to try the two piece for his Shrike.

With the standard weight carbine buffer, the gun runs fast (to say the least).
Figure that can't be good.

If my camera was not in the shop, I'd take photos.

FWIW
Your photo makes it look like the roll pin for the plastic bumper is backing out.
Mine were doing that and hanging on the spring during assembly (and probably during firing as well),
so I rolled over the ends over with a tapered punch and filed things flush.

I've never seen a buffer in that shape that did not come out of a Shrike!

JT
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Old February 21, 2016, 11:49 AM   #6
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Quote:
Originally Posted by Machineguntony
Should I get an H2 or H3? How do I know if I should be using H2 or H3? Is there a test?
There's no way to know for sure without trying it. An H2 buffer would almost certainly work, but an H3 might work even better. But it's also possible that an H3 buffer would be too heavy and the gun will short-stroke.

Like 2damnold4this said, you just need to test it out. Try an H3 buffer, and as long as rifle cycles properly and the bolt consistently locks back on an empty magazine, you're good. If it doesn't, go with the H2.

Also, keep in mind that you should make sure it runs properly without the silencer if you plan to shoot it that way. My LMT is going to be my primary HD rifle, so I want it to be as reliable as possible in every configuration I could possible shoot it. So I need a buffer that will work even without the silencer and with the rifle really dirty. However, if this was just a range gun that I shot only with a silencer, I could afford to go with an even heavier buffer; it might not work without the silencer, but it would be even smoother with it.

I suggest buying both an H3 and an H2 and testing them out. You'll probably find a use for the other one down the road. Some people will suggest only buying an H3 and if you need an H2-weight buffer you can just switch out some of the internal weights from your current carbine buffer. I don't like this because then you can't just look at the head of the buffer to see which kind of buffer it is, but to each his own. I suppose you could figure out a way to permanently mark it.
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Old February 21, 2016, 02:16 PM   #7
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Looks like the buffer is beat to snot. Something one would expect to see in a seriously over gassed scenario. Changing the buffer won't correct the over gassing.
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Old February 21, 2016, 05:44 PM   #8
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DUDE!!!!

That buffer is In BAD shape. Lol

I would buy a H3 buffer and try that. I doubt you will have problems with that setup. If you do then swap out 1 weight and you have a H2 to try out. You can engrave "H2" or whatever on the face of the buffer and know what's inside just by cracking the gun open and looking inside

Another option, and prob a better one, would be to go with an adj gas block. With that you can fine tune the gas to optimism function. Some of the adj gas blocks have an " off " position turning the gun into a single shot. This makes for the quietest rifle possible.

I know a full auto with the gas turned off seems oxymoronic, but some gas blocks allow easy and fast changing of the settings. Run the gun full auto, and then if you want to get as quiet as possible....shut off the gas
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Old February 21, 2016, 07:18 PM   #9
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Quote:
I'm guessing that you're using a lightweight carbine-weight buffer because that's what comes with most buffer system/stock combo packages. A carbine buffer is way too light for your setup; the full-auto and the short barrel don't help, but the biggest thing over-gassing your gun is the silencer. Your BCG is unlocking too soon and slamming way too hard against the back of the buffer tube, and that's why the end of your buffer is all beat up. You need an H2 or an H3 buffer. Not only will a heavier buffer slow down the cyclic rate, making the gun more controllable and greatly reducing parts wear, but it will also lower the amount of gas you get in your face.
That is very interesting and I like your analysis. Would a Tubb carrier weight system help in delaying the unlock? http://www.davidtubb.com/carrierweight-ar15 I am using them in my match AR15's, but these rifles are full sized AR15's with everything full sized.
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Old February 21, 2016, 11:16 PM   #10
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Thanks fellas. I freely admit that I'm an urban commando. I shoot these guns and share them with people because I enjoy and support the shooting sports. I am not an AR/M16 expert.

Mobuck mentioned that changing the buffer will not fix the overgassing situation. I thought changing out the buffer slows down the bolt, thus holding more of the gas in the chamber and gas tube longer, thereby helping with the overgassing situation. If changing out the buffer tube won't help with the overgassing situation, what will solve that problem?

I don't think I want to go with an adjustable gas tube. Turning the gun into a single shot isn't ideal.

I do run this gun in F/A a lot, just because I like it. That explains the beat up buffer. And in F/A, it runs really fast. It's probably killing the buffer.

I'm going to make my regular range gun another gun after I fix up this M16. I do enjoy the short 11.5 inch barrels, so I'll have to find another 11.5 inch barrel to go with my newly designated range gun. The 16 inch barrel with silencer is too unwieldy.
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Old February 21, 2016, 11:50 PM   #11
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Quote:
Originally Posted by Slamfire
Would a Tubb carrier weight system help in delaying the unlock?
It seems like it would, but I have no first-hand experience with that product.
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Old February 22, 2016, 12:04 AM   #12
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Quote:
Originally Posted by Machineguntony
Mobuck mentioned that changing the buffer will not fix the overgassing situation. I thought changing out the buffer slows down the bolt, thus holding more of the gas in the chamber and gas tube longer, thereby helping with the overgassing situation. If changing out the buffer tube won't help with the overgassing situation, what will solve that problem?
What he means is that you're fixing the symptoms of your problem and not the root cause.

The rifle combined with the silencer is putting too much gas into your system. So the heavier buffer is counteracting that extra gas. But to fix the root cause you need to figure out a way to not have all that extra gas in the first place.

The solution to that is to get an adjustable gas block. I'm not a huge fan of adjustable gas blocks on DI rifles because I've seen a few that didn't work well or managed to adjust themselves. Personally, I prefer the simplicity of just throwing in a heavier buffer. But if you're willing to play around with an adjustable gas block -- and especially if it's just a fun range gun and you're willing to take a chance with durability -- that could be a better overall solution.

Quote:
Originally Posted by Machineguntony
I don't think I want to go with an adjustable gas tube. Turning the gun into a single shot isn't ideal.
The purpose isn't necessarily to ever shut the gas off completely, it's to be able to tune the gas system so it has the optimal level of gas and no more.
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Old February 22, 2016, 01:11 AM   #13
Machineguntony
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I'm with you on this, Theo. I'd prefer to keep it simple and just use a heavier buffer. I understand what you're saying. So if I just use a heavier buffer and don't use a gas block, will that damage or put stress on the lower, due to the excessive gas in the system?

If the only cost of excess gas is to put stress on the upper and requiring a regular buffer change, I can live with that. I just don't want stress on the lower.
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Old February 22, 2016, 02:18 AM   #14
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I can't imagine how it could put any extra stress on the lower, other than getting it dirtier than normal.
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Old February 22, 2016, 08:04 AM   #15
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The heavier buffer only delays the cycle but won't reduce the battering of the buffer at the end of the cycle if there's a serious over gassing problem.
Just my opinion but I'm sticking to it.
If you're not tearing rims off, delaying the cycling isn't the answer.
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Old February 22, 2016, 10:16 AM   #16
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Quote:
Originally Posted by Mobuck
The heavier buffer only delays the cycle but won't reduce the battering of the buffer at the end of the cycle if there's a serious over gassing problem.
That's not true at all. A heavier buffer will greatly reduce the battering of the buffer at the end of the cycle since it slows the initial velocity of the carrier and the buffer. Remember, when you have the proper weight buffer the gas pressure has dropped significantly by the time the bolt unlocks.
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Old February 22, 2016, 12:12 PM   #17
Machineguntony
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Here's video of this gun, with exactly the same set up and same silencer, before the buffer gave out. Notice the extremely fast cyclic rate. Is that a sign of overgassing? My silenced AR with a 16 inch barrel has nowhere near this cyclic rate.

https://youtu.be/XFH1uoKQ1e0
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Old February 22, 2016, 12:59 PM   #18
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Quote:
The use of suppressors on rifles creates yet another dynamic in firearms design that is not commonly understood or communicated. Consider the suppressor on a firearm the same as a muffler on a car. The suppressor works as a filter for the gas (noise) that is escaping the barrel during firing. As a “filter”, it takes longer for the gas to leave the confines of the firearm, and thus, it creates back pressure. This back pressure, ESPECIALLY in a gas operated firearm forces an extensive amount of gas back through the firearm’s operating system that may create too much thrust too early during the firearm’s cycle of operation.

To counteract this back pressure, the use of an adjustable gas system is advised. By metering the gas system to ensure that it will cycle the firearm correctly and not flood the system with gas/pressure, the gun will work properly and will still benefit dramatically from the increased velocity potential of Superformance ammunition.
http://www.hornady.com/ammunition/su...rated-firearms
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Old February 22, 2016, 08:18 PM   #19
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"Remember, when you have the proper weight buffer the gas pressure has dropped significantly by the time the bolt unlocks."

That debate can rage for days. I doubt the milliseconds that the heavier buffer delays cycling will make so much diff if the extractor isn't tearing rims as run currently.
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Old February 22, 2016, 11:19 PM   #20
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https://alamotacticalreviews.com/201...for-the-ar-15/

Quote:
Proper buffer weights will result in a smoother functioning rifle and prolonged service life of parts. It keeps the rifle in battery slightly longer so the extractor has an easier time doing its job, and has more inertia bringing the bolt forward ensuring more reliable chambering of the next round.
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Old February 23, 2016, 01:42 AM   #21
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https://gunsmagazine.com/buffer-stuff/

Quote:
Carbine-length systems, in particular, can produce problems. Essentially, if too much [gas] gets in too soon, the bolt will unlock too soon as the system begins moving the bolt carrier to the rear. Then, the cartridge case gets yanked while it’s still expanded inside the chamber. This creates the “extraction” problems common to carbines (16″ or shorter barrel). It’s not an extraction problem, really, but a timing issue.

Additionally, an overdose of gas creates overly high-bolt carrier velocity going back against the buffer. It can get so high, and again this is most symptomatic in carbines, that the carrier will “bounce” off its rearward stopping point and rebound overly quickly, going back ahead.
[...]
We are in milliseconds with respect to “fast” and “slow.” Virtually all the influential firearms functions, including breaking a shot, are measured in milliseconds.

So, there is help for all this; altered port locations and sizes (only done on custom re-barreling projects) or regulated gas blocks—or both—make big differences. So, too, do heavier-weight carriers. Those resist initial movement for a speck longer, giving internal pressures longer to subside. The easier means are related to the “back part” of the system, which, let’s say, is the buffering apparatus. It can be altered to influence bolt carrier movement, in both directions. The direction that matters most is going back after firing.
[...]
Increasing buffer weight is effective. Doing this softens carrier movement rearward. The more weight, the harder to push.
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Old February 23, 2016, 01:50 AM   #22
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Quote:
Originally Posted by Machineguntony
Notice the extremely fast cyclic rate. Is that a sign of overgassing?
The more over-gassed your rifle is, the higher the cyclic rate is. So yes, that's definitely a sign of over-gassing.

That's one of the problems the military has when they add silencers to their rifles: The cyclic rate increases due to the extra gas back-pressure pushed back into the system by the silencer. That's one of the reasons that the military likes to use Surefire silencers; they're specifically designed to lower back-pressure, and one of the advantages of that is they don't increase the cyclic rate as much as traditional silencers.
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Old February 23, 2016, 08:13 AM   #23
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"Increasing buffer weight is effective. Doing this softens carrier movement rearward. The more weight, the harder to push."

This failed to include that "the more weight moving, the harder it hits(as in the buffer hitting the back of the tube)". Bigger hammer--bigger impact.
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Old February 23, 2016, 12:59 PM   #24
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Quote:
Originally Posted by Mobuck
This failed to include that "the more weight moving, the harder it hits(as in the buffer hitting the back of the tube)". Bigger hammer--bigger impact.
Sure, but when the force behind the heavier hammer is enough lower than the force behind the lighter one, the heavier hammer will have a lower impact.

When you have the proper buffer weight, your buffer hits the back of the buffer tube a lot more softly than when you have a buffer that's too light. And currently, Tony has a buffer that's too light. His bolt is unlocking too soon, and the carrier is going to the rear much faster because of two reasons: 1), the buffer is too light and therefore it moves faster, and 2) because the bolt is unlocking when the gas pressure is still super-high.

Adding a lighter buffer not only slows down the acceleration of the carrier, but it also allows the bolt to unlock a little later, and by that time the gas pressure has dropped a bit. So not only does a heavier buffer go the rear more slowly, but it also has less force pushing it to the rear in the first place. When Tony replaces his carbine buffer with an H2 or H3 buffer, it will hit the back of the buffer tube with a lot less force.
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Last edited by Theohazard; February 23, 2016 at 10:27 PM. Reason: clarification
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Old February 24, 2016, 07:26 PM   #25
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You know the way to answer these questions is to put some sort of device inside the buffer tube to determine how much the heavier buffer is slowed vs. a lighter buffer and how much force is exerted on the end of the tube. When these factors are given reliable numbers, the answers will be more than guess work.
I studied Physics in depth at an earlier time in my life and still remember parts of those studies. I think everyone will agree that a bigger hammer hits harder even though it's moving slower than a lighter hammer. Otherwise, the old timers would have been driving railroad spikes with a tack hammer(maybe a little stretch on the comparison).

Last edited by Mobuck; February 24, 2016 at 07:33 PM.
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