Slow fire M16 configuration?

[allotrope]

Many years ago I saw this now ancient video of a slow firing M16. Does anyone have any recommendations on how to replicate such a slow ROF with parts that are currently available? A lot has changed in nearly 17 years.

 

[amphibian]

My website my interest you: https://c3junkie.com/?page_id=1403

Below is my favorite way of slowing it down.  I also have a FerFrans rate reduction carrier but something about the timing feels off with the way it works.

[MPFiveO]

Generally, there are three ways to adjust the rate of fire in an AR style system. Add weight, choke off the gas, and mechanical delay.

Adding weight is easy. I had a bunch of spare buffers laying around and did some experimenting with the weights. I took a rifle buffer and basically filled it with tungsten weights from H buffers and ended up with something like an H12 instead of an H3. The amount of free movement replicated that of a standard GI buffer so the timing was not affected, not that you'd get bolt bounce with it. The ROF I got with it was nearly identical to using the Colt hydraulic buffer and green spring. You'd think so much weight moving back and forth would move the gun around a lot but it didn't, and the reason it didn't was that the bolt group was pretty much out of energy by the time the carrier made it all the way back. And one thing I did test was whether or not the bolt would lock back on an empty mag and it did every time. The only negative side effect was that the front face of the buffer developed a ring where it was pressing into the bolt carrier. So there was the formation of a step starting to protrude from the center of the buffer face. I'm sure at some point it would fail in some way because it's just too much reciprocating weight for the system as designed. A hardened steel buffer housing might solve that problem but I was working with what I had on hand.

The second way to slow it down would be to control the gas. The AR system doesn't have an adjustable gas system so one would have to be built and installed. This would not necessarily reduce reliability if tuned correctly but as designed the system is over gassed to be reliable. So, installing an adjustable gas system and choking it off would slow down the rate of fire.

A third way to slow it down would be by mechanical delay. Back in the day AAC made a rate reducer that had sliding weights on a central shaft. It used weight to slow things down but the distance the weights moved helped delay movement of the bolt group thus lowering the rate of fire. The AKM has a rate reducer built into the trigger group but I'm not aware of one that has been built for the AR trigger group.

The last way to slow things down would be with custom loaded ammo. Selecting a powder with a slower burn rate and lower pressure would slow down the rate of fire but it would take a lot of experimentation to achieve a reduction that didn't hamper reliability and safety. I don't recommend this route for safety reasons. Only an experienced reloader with familiarity of burn rates and pressures should attempt this method.

While I have experience with all of the above methods I've found that the Colt hydraulic buffer and it's own green spring to be the safest, most reliable, dependable and durable of any method of rate reduction. It's also a bit rare and expensive but it absolutely works, because engineering and all that science stuff. The only drawback to the Colt system is that eventually hydraulic buffers fail, either by leaking or blowing out a seal. The military doesn't care because your tax dollars pay for replacement and spare parts. But on the civilian side that is an out of pocket expense and the hydraulic buffers are rather costly.

For economical reasons, the adjustable gas block would be the way to go. It's not going to risk safety and it should be fairly durable. Reliability is adjustable so that's entirely on the operator.

So, in a nutshell, those are the options. I'm sure at some point someone will offer a better mousetrap.

[amphibian]

I have the AAC buffers but don't really consider them to be a 'true' mechanical delay.
I mentioned the Ferfrans already above.  That is a true mechanical delay.  As seen from the patent picture below, it has a sliding weight the that sear trip is mounted to. 

Large volume gas like the Fat Boy I mentioned above and the LaFrance Twin tube greatly increase the lock time and therefore drop the cyclic rate and do wonders when combined with restricting the gas flow.

Edited November 11 by amphibian

[smdub]

I tried to buy a Fatboy gas tube about a year ago(?) and everything lead me to believe they were discontinued.  Couldn't find an alternative.  Pigtail type tubes, etc all seem to be discontinued.  Figured I'd have to make my own someday w/ some cutting and welding..

[amphibian]

6 hours ago, smdub said:

I tried to buy a Fatboy gas tube about a year ago(?) and everything lead me to believe they were discontinued.  Couldn't find an alternative.  Pigtail type tubes, etc all seem to be discontinued.  Figured I'd have to make my own someday w/ some cutting and welding..

Yeah, I spoke to them last year and they were on the fence on bringing them back as they were expensive to make.  They were swaging them.  They only made them in Carbine length.  I had the pigtail and wouldn't recommend as they shrink under heat and then collapse on themselves.  Straight fat is the way to go.

I TIG welded my own for Mid and Rifle length.  Below is a 11.5 Mid I did.  I also did a 16" Rifle gas and suppressed with a custom large volume, I was like 450RPM, again with no gas to the face even suppressed, full auto.  I am working with another company to try to get some samples for re-sale.

[smdub]

Yeah, I'd prefer a mid length.  Though I'm sure I've got something around here w/ carbine gas I could use to test a short one.

Edited November 13 by smdub

[Gol03]

I had a problem with mine being too fast, I had a H buffer and 9mm buffer laying around so i tried them both. The H buffer was heavy enough so i could fire 2 or 3 round burst, which i ever wanted.