Changing cyclic rate


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o Unforgiven o
August 30, 2010, 08:21 PM
How do you go about changing the speed of a machine gun? I know that when building them the designers can to an extent change the rate of fire. How?

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zoom6zoom
August 30, 2010, 08:32 PM
The speed you refer to is called the cyclic rate. How it can be changed varies depending on the design of the gun. Many things can affect it, including weight of the reciprocating parts, spring strengths, size of gas ports to name a few... you really have to understand how the particular weapon system works first.

Sam1911
August 30, 2010, 08:39 PM
Evan, I've taken the liberty of moving your "slightly off topic" post in the belt-fed-thread to a separate thread of it's own, as I believe it is an interesting question and one deserving of some good answers.

I can think of several answers right off. One is that shortening the bolt travel raises the cyclic rate, in general. If you play with submachine guns much, you can get "buffers" that insert behind the bolt and reduce how far back it can travel. Of course this can negatively affect reliability -- but to a point, with many guns, you can get away with a noticeable reduction in bolt travel distance. The bolt doesn't go back quite so far, thus it doesn't take so long to go back and come forward, thus it all gets done quicker and the cyclic rate rises.

More traditional ways of regulating the cyclic rate would be lockwork adjustments that hold back firing of the next shot until "something" happens. The AKM has a device that acts as an out-of-battery fire prevention safety but it is more commonly thought of as a cyclic rate reducer or hammer retarder.

There are probably just as many different solutions to the question as there are gun designs. Hopefully some more knowledgeable members will chime in to explain some of them.

Sam1911
August 30, 2010, 08:42 PM
Here's a link to a thread on UZITalk.com regarding the effects of buffers in an Uzi (what else? ;)) with video of the results. http://www.uzitalk.com/forums/showthread.php?t=52517

Note, there's enough room in the receiver of an Uzi to reduce the bolt travel distance by 3/4", 1", and even 1-1/4"!

jmorris
August 31, 2010, 12:00 AM
Weight is the easiest. Here are the differences in bolt weight between a PS M10/9 bolt and a Cobray M10?9 bolt.

http://i664.photobucket.com/albums/vv5/qvideo/gn/DSC01917.jpg
http://i664.photobucket.com/albums/vv5/qvideo/gn/DSC01921.jpg
http://i664.photobucket.com/albums/vv5/qvideo/gn/DSC01922.jpg
http://i664.photobucket.com/albums/vv5/qvideo/gn/DSC01923.jpg

KingTiger
August 31, 2010, 09:53 AM
Those are some good examples jmorris. For my SWD M11/9, I have 4 different 9mm bolt weights that vary the cyclic rate between 1200 - 550 rounds per minute, and also a .22 LR bolt that runs between 800-900 RPM.

A suppressor tends to increase the cyclic rate due to back pressure.

taliv
August 31, 2010, 10:18 AM
for m16 pattern, you can use a pneumatic buffer

Carl N. Brown
August 31, 2010, 10:30 AM
For the Thompson M1928, the actuator (the part of the bolt with the bolt handle) was made heavier than that of the M1921.

SDC
August 31, 2010, 11:16 AM
As you can see above, it really depends on the particular design; you can use lighter or heavier bolts, heavier or lighter springs, smaller or larger gas ports, thicker or thinner (or more or less resistant) buffers, and on and on. Did you have a particular design in mind?

Blakenzy
August 31, 2010, 12:11 PM
BAR operation and rate of fire selector
http://www.youtube.com/watch?v=KA180Bfx478&feature=related

Part2
http://www.youtube.com/watch?v=5bt3VQrvBxU&feature=related

rcmodel
August 31, 2010, 12:50 PM
The early M16 had the cyclic rate changed (too fast) by accident when they changed from stick to ball powder. They changed it back with different powder again.
But it was still too fast, so the buffer weight was increased.

rc

gun guy
August 31, 2010, 01:31 PM
First, unless you are engaged in some mission specific operation, why on earth would you want to change the rate of fire. Already the rate of fire of the mac/cobray style weapons is an insane speed of 1,200+rpm. At this rate, hit probabilty is near 0, while ammo expanduture is horrific. In a nutshell, by the time you get your finger off the trigger, the gun will be empty, you will have missed your target, and have to call a time out in a gunfight to reload. 500 rpm is near perfect for a smg, if you wish to actually acomplish something other, than a fireworks display.

jmorris
August 31, 2010, 02:29 PM
First, unless you are engaged in some mission specific operation, why on earth would you want to change the rate of fire. Already the rate of fire of the mac/cobray style weapons is an insane speed of 1,200+rpm. At this rate, hit probabilty is near 0, while ammo expanduture is horrific. In a nutshell, by the time you get your finger off the trigger, the gun will be empty, you will have missed your target,


Most of the time you want to change the rate of fire to make it slower. Why is hit probability near 0? Even with the light PS bolt you can "single" an M10 on auto. They certainly don't go jumping all over the place. Click on this photo.

http://i121.photobucket.com/albums/o213/jmorrismetal/can/m10/th_VID00032.jpg (http://s121.photobucket.com/albums/o213/jmorrismetal/can/m10/?action=view&current=VID00032.flv)

He doesn't single but 3 round bursts the first two pulls.

PTK
August 31, 2010, 02:30 PM
So, gun guy... you have precisely zero experience with any Military Armament Co. made firearms, and you've gleaned that from what other people have said here and there?

MrCleanOK
August 31, 2010, 04:00 PM
M240 machinegun rate of fire is varied with a 3-position gas regulator between the gas port and the gas tube.

TexasRifleman
August 31, 2010, 07:17 PM
Already the rate of fire of the mac/cobray style weapons is an insane speed of 1,200+rpm. At this rate, hit probabilty is near 0, while ammo expanduture is horrific. In a nutshell, by the time you get your finger off the trigger, the gun will be empty, you will have missed your target,

I guess that's been shown so many times on TV and in movies, and repeated so often on gun forums, that it's become Gospel.

It's simply not true of course. Like any firearm the Mac's require skill and proper technique to be used effectively. In the hands of someone with experience shooting them I would not want to be on the receiving end. They can be quite devastating things.

gun guy
September 1, 2010, 02:50 AM
Actually, I have probably fired more automatic weapons, (I could go into everything from 3 in naval guns, the 40 mm with and without amplidyne power drive,on down to small arms made in the usa/europe/and comblock countries etc, but it would take quite awhile) than you have seen ptk, and in combat situations. You will notice the weapon in the picture has the added weight of a suppressor/extension, this does hold down muzzle flip, but you are adding more weight to an already morbidly obese handgun. At this point, a thompson with the stock removed is about the same size, and a far better weapon. I have found the best hit probability is with slower cyclic rates such as the uzi, or the h&k mp5 series. IMO the mac/cobray weapons look great on filim. In a tactical situation, the best use of those high cylic rate weapons, is to tie a string on them,,and toss them into the rooom. The results are about the same as trying hand fire them. But then, that was just my observation, after actually trying to use one, in combat vs standing on a range on a sunny day. We used to have a saying, never assume your safe from a machinegun, just because you are standing in front of one. As far back as ww1 Alvin York proved this by using aimed fire, to knock out machine gun nests that were hammering rounds at him. In a tactical setting, one man, with a mac can pour fire while the rest of the team takes targets of oppertunity. In a solo setting, only a fool, would attempt to engage a skilled opponent, with a full auto weapon, he would be out of ammo about the time things got truly interesting.

jmorris
September 1, 2010, 11:01 AM
but you are adding more weight to an already morbidly obese handgun. At this point, a thompson with the stock removed is about the same size, and a far better weapon. I have found the best hit probability is with slower cyclic rates such as the uzi, or the h&k mp5 series.

It’s a machine gun not a pistol even if it were semi auto it would be an SBR under NFA. In any case the obese MAC weighs less than either the Uzi or almost all of the variations of the MP5 (some of them even weigh more than the Uzi). I will agree with your last comment, heavier and/or slower rates of fire can help with accuracy, but then again we are talking about MG’s.

The MP5 SD is a very controllable SMG at almost 8 lbs but I have bolt action rifles that weigh less (including optics), talk about slower rate of fire and a noticeable increase in accuracy…

PTK
September 1, 2010, 11:04 AM
Frankly, gun guy, I don't believe you.

For what it's worth, here's his original message, sent via PM:

I actually had to lead a 4 man team armed with the 45cal mac weapons. What you have in reality is an overweight handgun, with lousy sights. It is mediocre at best in semi fire and for all purposes useless in full auto. Short controlled bursts, which anyone, who knows anything, about full auto weapons is virtually impossible due to the cylic rate. Full auto pistols are nothing new, and rarely used. As for the corbay knock offs, their poor metalurgy, and cheap design lead to hammer failures after about 350 rounds. As we made our way back to the USS Greyback, the only lpss in the fleet at the time, we tossed the macs into the drink. Although things may be different between a hot day at the range, and a hot day in the jungle.

Everyone please note that this "expert" just said that "Corbay" (would that be Cobray?) MAC styled SMGs have hammer failures. Open-bolt guns do not have hammers. ;)

Furthermore, what year are you alleging that you were running a covert op from a freaking missile submarine?

Grayback was initially designated as an attack submarine, but was converted to a Regulus guided missile submarine (SSG-574) in 1958.

The MAC-10 (Military Armament Corporation Model 10, officially the M10) is a highly compact, blowback operated machine pistol developed by Gordon B. Ingram in 1964.

Or are you just that super-secret, that you had this firearm with a team of men prior to it being developed?

For what it's worth, most SMG matches I've been to recently have been won or at the very least had extraordinary competitors (placing in the top 5, which is usually extremely close) using just the family of guns you're trashing. Or are they not skilled, or under stress? ;)


EDIT: Additional information, apparently he's quite the expert.

Tell me all about your actual combat experiences. As I look out across my cars, which I have posted pictures of, about 130k+ all paid for in cash, and my motorcycle collection, about another 30k all paid for in cash, I won't even go into my guitars, guns, and other babbles, all from money paid to me, for my knowledge of firearms and tactics, I know what my opinion is worth. If you are doing better, congrats, if you are still making car payments, and working some job other than the firearms industry, that pretty much tells you, what your opinion is worth.

My bad, I suppose that the mistakes about simple operation of firearms you're familiar with is due to vast experience.






EDIT 2: I would like to publicly acknowledge my mistake - the Grayback was used, post-1967, as a SEAL "Swimmer Delivery Vehicle". No offense intended or slight meant on that account. :)

Sam1911
September 1, 2010, 11:27 AM
Short controlled bursts, which anyone, who knows anything, about full auto weapons is virtually impossible due to the cylic rate.

This just doesn't make sense, and is DEMONSTRABLY untrue.

In fact, the video posted up in post 13 shows it being done.

That technique is pretty simple. I've taught it in two minutes to middle-aged houswives who'd never fired a sub-gun before.

Of course, that's the sort of thing you'd do on a range, but not in the jungle ... supposedly. :scrutiny:

PTK
September 1, 2010, 11:29 AM
I'm still at a loss as to why you wouldn't use controlled bursts in combat...

jmorris
September 1, 2010, 11:43 AM
I'm still at a loss as to why you wouldn't use controlled bursts in combat...

I have absolutely zero combat experience but controlled bursts are a better method for popping balloons floating across the pond than just hosing.

JamisJockey
September 1, 2010, 02:53 PM
You're using your "experience" as a stick, with which to beat down any opposing viewpoint on the use of an SMG. And nobody cares about your "stuff". Also, your stuff doesn't prove anything.
By the way, are you perhaps a bodybuilder?

KingTiger
September 1, 2010, 04:34 PM
Here's a friend of mine shooting my M11/9 w/Lage Slow fire bolt. He had never shot a MG before. The first shot is a single, and there's another one further into the clip. Looks like he's doing the "impossible". :neener:

http://i183.photobucket.com/albums/x119/KingTiger_photo/th_Creekside6_20_08008.jpg (http://s183.photobucket.com/albums/x119/KingTiger_photo/?action=view&current=Creekside6_20_08008.mp4)

JamisJockey
September 1, 2010, 05:27 PM
Your video is obviously a fake, because an "Operator" said that it can't be done! Don't you see all the money he's spent on cars and motorcycles to prove you wrong? I'm sure that super long 4 round burst in the middle of the video made the weapon uncontrollable.

jmorris
September 1, 2010, 06:48 PM
MAC 10/45 bursts

http://i664.photobucket.com/albums/vv5/qvideo/7409/th_bwm1045.jpg (http://s664.photobucket.com/albums/vv5/qvideo/7409/?action=view&current=bwm1045.mp4)

http://i664.photobucket.com/albums/vv5/qvideo/7409/th_branm1045.jpg (http://s664.photobucket.com/albums/vv5/qvideo/7409/?action=view&current=branm1045.mp4)

Even a kid hosing a 45 MAC for the first time isn't all over the place.
http://i664.photobucket.com/albums/vv5/qvideo/7409/th_twm1045.jpg (http://s664.photobucket.com/albums/vv5/qvideo/7409/?action=view&current=twm1045.mp4)


If you really want to talk about high rates of fire you can even burst full auto Glocks.

http://i664.photobucket.com/albums/vv5/qvideo/7409/th_glock18.jpg (http://s664.photobucket.com/albums/vv5/qvideo/7409/?action=view&current=glock18.mp4)


Even hosing as light as they are, still easy to control.
http://i664.photobucket.com/albums/vv5/qvideo/7409/th_mglock18.jpg (http://s664.photobucket.com/albums/vv5/qvideo/7409/?action=view&current=mglock18.mp4)

9mmepiphany
September 1, 2010, 06:51 PM
I will say that I haven't the experience with the M-11/9...that one is quite decked out with the shoulder stock and foregrip...but I have had experience with the M-11 (.380) and the M-10 (.45)

The M-11 was very pleasant and controllable in burst fire.

The M-10 did take a little practice to get 2-3 controlled rounds on target, but it was really a lot of fun, and very controllable, when you added a suppressor

jmorris
September 1, 2010, 06:54 PM
Here is the MP5 and M16 with the tacticool forward grip, as you can see it's more about the shooter than the gun.

http://i664.photobucket.com/albums/vv5/qvideo/7409/th_mp52.jpg (http://s664.photobucket.com/albums/vv5/qvideo/7409/?action=view&current=mp52.mp4)

http://i664.photobucket.com/albums/vv5/qvideo/7409/th_cman16.jpg (http://s664.photobucket.com/albums/vv5/qvideo/7409/?action=view&current=cman16.mp4)

jmorris
September 1, 2010, 06:58 PM
I will say that I haven't the experience with the M-11/9...that one is quite decked out with the shoulder stock and foregrip


All of the M10 SMG's came with the wire stock the foregrip is just a can I built with K's to look similar to the Sionics, and still much more compact than the MP5.
http://i121.photobucket.com/albums/o213/jmorrismetal/can/m10/maccan.jpg

jmorris
September 1, 2010, 07:00 PM
As you can see here even a stocked Glock is about the same length as a short barrel M16.

http://i664.photobucket.com/albums/vv5/qvideo/7409/HPIM0327.jpg

gun guy
September 1, 2010, 07:41 PM
well gee, by 1974, when i was there, the mac had been around for about what, 10 years, and the greyback wasn't hauling missles anymore,,,what did you say it was hauling, highly trained operatives? :) thanks for verifying what I said. sorry about the typo with cobray.

PTK
September 1, 2010, 07:46 PM
well gee, by 1974, when i was there, the mac had been around for about what, 10 years, and the greyback wasn't hauling missles anymore,,,what did you say it was hauling, highly trained operatives? :)
Funny how you focus on the one issue that "proves" you right, whilst glossing over the glut of mistakes, false experiences, et al.

TexasRifleman
September 2, 2010, 08:37 AM
The OP asked the hows and whys of changing cyclic rate and that was well answered by several folks. The rest is a debate on the usefulness of some types of subguns. That's deserving of it's own discussion if done thoughtfully and politely, it's a long debated topic for sure.

If you enjoyed reading about "Changing cyclic rate" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!