AK 47 MG Question

**Wayne** · July 9th, 2010, 10:45 AM

Awhile back I was watching a TV program about the age old question of AK vs M16. They went into the design of each, rate of fire, cartridge size and what not. Being an engineer myself (don't know anything about full auto) my interest was peaked by the difference in rpm. Why does the ak shoot at 600 rpm vs the M16 at 800 rpm? They also mentioned some ak's have a rate reducer and some don't. What is the rpm with a rate reducer vs without. Does the M16 have a rate reducer?

My brother was in a rifle platoon in Vietnam. He told me that the M16 was so fast on full auto that carrying enough mags was a big problem and therefore was used on full auto only in certain situations. The fast M16 with a 20rd mag vs a slower ak with a 30rd mag. Seems the commies out thought us. Just wondering....thanks.

**Nate7667** · July 9th, 2010, 12:56 PM

It comes from a few different things that all play a part for the final outcome.
-the overall design or type of gas/recoil system
-length of gas system, which will effect dwell time and lock up time, not much but it does
-weight of bolt, the gas has to push something, either the piston or the bolt
-amount of gas used to push said bolt. this is where the reducer come into play.
-any amount of back pressure will increase the rate of fire, like a suppressor
-some different buffers will increase the rate as well. may short stroke the bolt and not allow it to travel is entended length in turn speeding up the rpm

im sure someone will add some more info or correct me

**Hawk** · July 9th, 2010, 01:28 PM

I really don't see much of a difference between 10 rounds a second (AK) vs 13 (M16).

Correct me if I'm wrong but isn't F/A for suppressing fire & S/A for when you want well aimed accurate fire?

**Nate7667** · July 9th, 2010, 01:51 PM

Originally Posted by Hawk

Correct me if I'm wrong but isn't F/A for suppressing fire & S/A for when you want well aimed accurate fire?

Probably, until you have been thrust in to a jungle on a different continent half way around the world at age 18.....then you just dont let go of the trigger. LOL

**ungawa** · July 9th, 2010, 05:12 PM

In both intermediate rifle calibers and handgun calibers almost everybody finds that 800 rpm is more controllable than 600 rpm or less. When comparing the two rates of fire in the same gun. There are exceptions, but it holds true across a wide range of firearms of all different configurations.

That is not an AK vs. AR comparison, just providing insight on that one question.

**PA Rifleman** · July 10th, 2010, 09:31 PM

Originally Posted by Wayne

... What is the rpm with a rate reducer vs without. Does the M16 have a rate reducer? ...

The so-called "rate reducer" is something of a misnomer, it's more like a second trigger mechanism. Machine guns that are hammer-ignited (the M16 & AK are) have a unique requirement, and that's a means of preventing the hammer from releasing when the bolt's out of battery. If humans could match the bolt speed perfectly, we could fire semi-autos as machine guns. In reality, most people cannot, although some folks simulate this with a technique called bump firing.

In an M16, this is called the auto sear, and it's simply a tab that trips the hammer when the bolt closes. This feature isn't necessary in a semi-auto rifle.

Since the auto sear is a critical component to make this type of machine gun work, it's viewed as prima facie evidence of intent to make or possess a machine gun. For those persons in possession of a registered machine gun, it's a non- issue. (See BATFE regulations - link)

Here's an auto sear in an M16 receiver:

M16 auto sear.
Click on image to enlarge.

The AK has a similar device. Machine guns that fire from a fixed firing pin (STEN, MP-38 -40, MAC-10, -11, UZI, etc) do not have nor use an auto sear since they do not have a hammer. They use a technique called advanced primer ignition which is self-synchronizing.

**ungawa** · July 10th, 2010, 09:49 PM

Originally Posted by PA Rifleman

The so-called "rate reducer" is something of a misnomer, it's more like a second trigger mechanism. Machine guns that are hammer-ignited (the M16 & AK are) have a unique requirement, and that's a means of preventing the hammer from releasing when the bolt's out of battery. If humans could match the bolt speed perfectly, we could fire semi-autos as machine guns. In reality, most people cannot, although some folks simulate this with a technique called bump firing.

In an M16, this is called the auto sear, and it's simply a tab that trips the hammer when the bolt closes. This feature isn't necessary in a semi-auto rifle.

Since the auto sear is a critical component to make this type of machine gun work, it's viewed as prima facie evidence of intent to make or possess a machine gun. For those persons in possession of a registered machine gun, it's a non- issue. (See BATFE regulations - link)

Here's an auto sear in an M16 receiver:

M16 auto sear.
Click on image to enlarge.

The AK has a similar device. Machine guns that fire from a fixed firing pin (STEN, MP-38 -40, MAC-10, -11, UZI, etc) do not have nor use an auto sear since they do not have a hammer. They use a technique called advanced primer ignition which is self-synchronizing.

I've run my M16 at all kinds of rates of fire, up to 1000. Including about 200 RPM - which was really amazing, didn't think it could run that slowly and still chamber rounds. These were with mixes of buffers and varying bbl/gas system lengths. Of course, there are several adjustable gas systems for the M16 that can change ROF without reconfiguring.

Also have run M11/9 at rates from 600 rpm to 2000 rpm. Everything above 1200 was with stock-type (not stock) uppers with extra/larger buffers added. It's a hoot. For the guns I have shot, everything below 1000 was with Lage uppers and rate of fire varied by bolt weight.

UZI - I have fired them at 600 up to almost 1000 rpm. Buffers.

Of course, ammo can also change rate of fire. Weak ammo increases rate of fire in open bolt weapons. Not sure why it doesn't in the M16, kinda weird.

In most common individual MGs that are OB or somewhat customizable you can often choose ROF.

**Wayne** · July 12th, 2010, 11:40 AM

In my original post I stated that I was an engineer. That is, a chemical engineer. I better stick with what I know! All of the posts were very informative and interesting. I have often heard or read the "fires from an open bolt position". I had no idea what it meant until now. Also, regulating the gas pressure, and buffers. Very interesting. Thanks everyone.