Firearm & Gun Forum -

Firearm & Gun Forum - (
-   General Shotgun Discussion (
-   -   Recoil vs Gas Operated? (

Cryptic 07-25-2007 04:05 PM

Recoil vs Gas Operated?
What is the better and why?

robocop10mm 07-25-2007 09:51 PM

Recoil vs gas
They have their own benefits. Recoil operated shotguns are less prone to malfunctions due to fouling. They are generally simpler to manufacture. The Bennellis do not like light loads. They only work with high brass type stiffer loads.

Gas guns have softer recoil. They "can" be more prone to fouling. The gas systems have to be regulated to work with the load. "Some" have a fairly narrow range of loads that work. The remington 11-87 adjusts its self to a fairly wide range of loads. My Saiga seems to eat whatever I feed it.

quique 09-10-2008 10:00 PM

recoil vs gas
im not sure i understand. gas operated means that the gas produced by the burnt powder moves a mechanical piston that pulls back the slide (ejecting the spent cartridge) and then the slide by action.reaction moves back front (loading the new cartridge from the mag).

recoil operated means what exactly? recoil is produced by the same expanding gas. so what is the difference?

pls explain

RL357Mag 09-11-2008 02:12 AM


Originally Posted by quique (Post 40006)
im not sure i understand. gas operated means that the gas produced by the burnt powder moves a mechanical piston that pulls back the slide (ejecting the spent cartridge) and then the slide by action.reaction moves back front (loading the new cartridge from the mag).

recoil operated means what exactly? recoil is produced by the same expanding gas. so what is the difference?

pls explain

In a recoil system, inertia is used to cycle the action and load the next round. In a gas system, some of the combustion gas is bled-off to cycle the action.

quique 09-11-2008 02:36 AM

but isnt that the same?
the inertia that moves the slide back is generated by the expanding gases, isnt it?

h2oking 09-11-2008 08:29 AM

The explanations posted are close to explaining the difference between recoil operated and gas operated but I will try clarify the difference a little better. I cannot think of any gas operated gun that the bolt or slide depends just on gas to push it to the rear. Rather the gas is only utilized to unlock the bolt and then inertia and momentum of the recoil takes over completing the cycle just like in a recoil only operated gun, it continues to move the bolt to the rear compressing the recoil spring that sends the bolt back into battery picking up a new cartridge along the way and chambering it. How the gas gets to the unlocking of the bolt in a rifle is via a very small hole that is is drilled through one side of the barrel usually located somewhere in the second half of the barrel toward the muzzle. At this hole location there is usually some type of fixture attached to the barrel that connects to a small steel tube that transports the gas to a piston that is connected to a mechanical part that unlocks the bolt. On most gas operated shotguns there is no steel tube but rather there usually is a sliding piston that is fitted around the magazine tube and the fixture that attaches the barrel to the magazine tube transports the gas to the piston which pushes the charging bar just like on a pump gun unlocking the bolt and then inertia takes over as described above. In most but not all recoil operated guns the inertia of the recoil is what unlocks the bolt or slide. As an example almost all recoil operated semi auto pistols work like a 1911 Colt whereby as the slide starts to move back ever so slightly from recoil the back of the barrel drops down unlocking the barrel from the slide allowing the slide to move all the back. There are recoil operated guns that their bolts or slides do not lock and only depend on the recoil spring and the weight of the bolt to keep it closed long enough to allow the bullet to get out of the barrel before the bolt opens. These type of guns are sometimes referred to as "delayed" blow back guns which is really a bit of a misnomer because without that feature of the bolt remaining closed or "delayed" until the bullet leaves the barrel in either case of a gas or recoil operated gun the brass would blow up outside of the gun because of the pressure of the gas pushing on the bullet would also be pushing against the walls of unsupported brass if the bolt were to open too early. Some guns like a Thompson sub machine gun fire on what is called an open bolt meaning that the gun is in the ready to fire mode when there is no bullet in the chamber and the bolt is pulled to the rear. When the trigger is pulled it releases the bolt allowing it to travel toward the chamber and along the way it picks up a round firing it simultaneously as the round chambered. In this case it is the forward momentum caused by the weight of the bolt that keeps the bolt closed just long enough to allow the bullet to leave the barrel. On the 1921 and the early 1928 Thompsons there was a machined slot on the bolt that accommodates a bronze saddle to fit over it. This bronze saddle caused a friction that locked the bolt for just a millisecond to insure the bullet had left the barrel. That system is called the Blish system named after its inventor. I know of only one other gun that uses a modified version of that principal and that is the very classy and expensive Cosmi shotgun made in Italy. I probably told you all more than you wanted to know, but oh well...

I hope that helps, Ron

janikphoto 09-12-2008 02:25 AM


Originally Posted by quique (Post 40054)
the inertia that moves the slide back is generated by the expanding gases, isnt it?

I know the post above went into great detail, but let me say the abridged version...

All ammunition releases a gas, but that's not what you should focus on. It matters where the gas goes to answer your question. In a recoil operated system, it's basically a force from the shell directly pushing on the bolt. The gas operated system takes gas from in front of the casing, diverts it from the barrel and into a piston. This piston is then pushed back by the gas. The piston is attached to an operating rod, which is attached to the bolt. You see where the difference is now?

Virginian 09-27-2008 08:58 AM

In a gas operated gun a tiny bit of the expanding gases is bled off to operate the action. Because of the way the different components of the gun get in motion at different times and rates, it tends to greatly mitigate felt recoil. The gas does not just unlock the action, it operates it. You can hang a gas gun from a string and it will fully function when you pull the trigger. Because some gas is used to operate the action, and these gases are at best somewhat dirty (Blue Dot gas is downright dirty), a gas action will need to be cleaned. The frequency depends on the design to some extent. I clean my guns anyway so to me it has always been a non-issue.
In a recoil operated gun, the recoil gets the whole gun moving backwards. You must provide resistance to make things work. The easiest to explain is the Browning long recoil action. After firing, You slow the stock and receiver down, and the entire barrel and bolt move all the way to the rear position locked together, compressing the action spring as they go. At that point they unlock, and the barrel moves forward, leaving the bolt to the rear, and ejecting the spent shell casing. When the barrel is in battery, it releases the bolt, which moves forward picking up a new shell, and pushes the shell into the chamber and locks itself to the barrel again. Different recoil actions function a bit differently, with less stuff moving so far, but that's the basic principle. All shotgun recoil operated actions have the barrel and bolt locked together until well past when the peak pressure has occurred, and the charge is gone from the barrel. "Inertia" is a sales tool term, because 'recoil' has some unpleasant connotations. Shoot a Benelli 3-1/2" 12 gauge and you will see that "Inertia" can be worse than plain old recoil ! The recoil actions are "cleaner" because they do not get exposed to anything but residual gasses and residue from the empty shells being flung out, so they do not require cleaning as often. Just when or why not cleaning your guns came into vogue, or why, I am not sure.

h2oking 09-27-2008 05:57 PM

Virginian: It never ceases to amaze me how some people think. Go get yourself an AK 47, an SKS or an AR 15 and take a look at how the action works. Once the action is unlocked there is no pressure available to continue to operate the action. Pressure from the gas is only used to unlock the gun then recoil takes over exactly as I said. Then I when went on to say I cannot think of any gas operated gun that actually operates the action doesn't mean there isn't one, it means I can't think of one. Can you? Not to be a smart ass, but did it not occur to you from reading my post that I have a great deal of knowledge and experience with various types of firearms? Did you even know what the Blish system is before reading my post? Have you ever even heard of a Cosmi shotgun? How do you think an HK Squeeze cocker works? It has a gas port and a piston and yet it is not gas operated at all, rather the recoil is retarded by gas as opposed to the recoil spring. If you pull the bolt out of an AR 15 you will see snorkel attached to the bolt that fits over a steel tube that runs to the front sight from where it gets gas. Once that snorkel moves away from that tube is open to the atmosphere meaning all gas pressure is gone and this happens just as the bolt rotates and unlocks all caused by gas but that is where it ends. I am sitting here with an SKS in my hands and the gas piston pnly moves far enough to unlock the action. If you think I am wrong please explain to me and others here how and why you think that the gas operates the action other than your hanging the gun on a string theory. Though I understand what you are trying to portray with your theory it has about as much to with what we are talking about as who won last nights ball game.:)

Virginian 09-28-2008 12:27 AM

Okay, I am not going to be a smart ass, and I can do it without making any snide comments, but I know more than a bit about guns and the physics of motion myself. I regret that I did not clarify that I was talking shotguns only, since this is a shotgun forum, but with that caveat, I stand behind everything that I said. I have heard of the Blish system, but it was long ago and I did not even remember the connotation. It is I take it a purely recoil action?
I take it that you do not agree that in order for an action to be recoil operated, that the mechanism has to be moved to the rear completely by the forces generated by the charge and gases exiting the front of the gun barrel. I think that's where we differ. Because if you take say a Remington 1100, and instaed of hanging it from a string, lets anchor it so it cannot move, it will still function (until the recoil obliterates the stock). Now in my vocabulary, that means the action is totally gas operated. If you are talking about the fact that the gasses unlock the bolt and get the action assembly moving in a short gas cylinder, and then the momentum of the moving parts continues to carry them to the rear, and then the action spring powers the return and reloading operations, and you are calling everything after the initial push from the gasses recoil operation, then we have a simple semantics issue. It might more correctly be called gas/inertia action, but that term has been previously appropriated as already alluded to. I call it gas operated, and so does most of the world. And, all gas operated semi autoloading shotguns that I can think of use some variation of the same sequence.

All times are GMT. The time now is 06:08 PM.

Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.