As long as I did a sorta tip and info thing on recoil operated shotguns, I had been thinking of doing the same for gas operated shotguns as well. All the incentive I needed was a request, which arrived today so here is some information on gas operated shotguns and a couple of tips to take care of common malfunctions.
I'll speak mainly of the Remington 1100 which has been around for a long time, and is a basic gas operated gun. A few other common guns that are gas operated would be the Ithaca 51, the Browning Gold , Winchester Super X 2 , etc.
Problems with the gas operated systems in these guns are often times the cause of malfunctions that are simular in nature to the recoil operated shotguns. That is to say , failure to eject or completely eject the empty - stopping the shooting cycle. (jam)
Like with the recoil operated guns you first should understand the mechanics of the gas operated gun. In order to operate the shooting cycle the gun has a gas piston system that is acted upon by the gas pressure behind the shot/slug that is traveling down the barrel after firing. This is accomplished by having a hole or holes in the barrel that allow the gas to bleed into the gas system forward of the piston assy . When the shell goes off, the bolt is locked to the barrel and the pressure of the exploding gases drives the gas piston rearward. The piston drives the operating rods that control the bolt carrier mechanism . As the bolt and carrier travel to the rear, the bolt unlocks from the barrel ,(On gas guns this unlocking happens early in the shooting stroke) as the bolt completes its rearward travel ,it will eject the empty through the ejection port , and allows a fresh round to be fed upward into the chamber on its return forward stroke powered by the action spring.
Now to the control of this function : In order for this cycle to be smooth, and in control, the mechanism employs either a fixed or metered gas control eliment. In the case of the 1100 it is a fixed sytem so we will talk about that first. The gas hole in the barrel of the 1100 is located inside the barrel extension. The magnum barrel has a single hole and the non-magnum barrel will have a double hole. This is the only control the 1100 has for metering the amount of gas pressure used to function the shooting cycle. Since magnum loads creat more pressure, the single hole is used on magnum guns.(3 inch chambers) With the reduced pressures created by non-magnum loads, the barrels chambered for 2&3/4 inch loads uses a dual hole system to feed more gas into the system. Both magnum and non-magnum barrels will shoot a "range" of loads within the operating perameters of the gun..
So now we come to our first method of controling the function - that is the choice of ammo we use. The heavier the load - the more gas/pressure that is provided to operate the shooting cycle. If not enough gas/pressure is created to drive the piston rearward the gun will not have sufficient speed, power, or length of stroke to complete the shooting cycle. If too much gas is provided , then we are once again beating and slamming our gun to an early death - and abusing our shoulder as well.
Here again worth mentioning , when buying a used 1100 you should look for buffer damage. The buffer on the 1100 is a nylon material either black or cream colored and it is located on the rear of the bolt surrounding the back of the firing pin. They will all mush a bit but should not have cracks or chips out of the buffer. They are not hard to change out on this gun so don't let a broken one change your mind about purchase if the price is right. Let it however be a bargining chip on your side and also make you aware that the gun has likely been slamming a bit from perhaps shooting short magnums in a non-magnum gun. I have yet to see a cracked bolt on a 1100.
The gas piston & common problems : On most of the 1100's there is basically a three part gas piston and seal* . The piston sits just forward of the action bar sleeve on the outer surface of the magazine tube. It's concave surface facing forward. The piston seal which is also made of metal sits just forward of the piston, with it's convex surface toward the rear of the gun and facing the concave surface of the piston. Forward of these two parts is the barrel seal which is a special rubber type o-ring . This o-ring prevents gas from excaping the system through the front of the barrel extension. The most common problems in this system are : 1.) residue build up on the magazine tube and piston , 2.) A worn out o-ring seal. 3.) Improper assy of the gas system. I might mention here that cleaning of this system should also include cleaning the gas hole or holes in the barrel.
* Note : The later manufactured 1100's have a one part sytem that replaces the piston and the piston seal on the these guns. You can no longer buy the individual piston or piston seal from Remigton. The o-ring barrel seal remains the same.
Onward to metered gas systems : Pretty much all other gas operated shotguns I can think of have a metered gas system. (there are a couple exceptions) This system varies in design from manufacturer to manufacturer, but they all do the same thing. In an attempt to allow the gas operated shotgun to shoot a wider range of loads from light to magnum , the design of a metered gas systems uses a gas bleeding system. That is to say , they use less gas to operate the shooting cycle and "bleed" off the excess gas created by heavier loads. In the case of the 11-87 for example this is simply done by placing a bleeder hole in the barrel extension and sealing the front of this hole with a spring loaded washer . Once the pressure builds to what is needed to operate the shooting cycle the spring/washer is pushed open/away from the front of the bleeder hole, and the excess gas excapes. By doing this the gun can handle a much wider range of loads up through the magnums without developing excess pressure on the operating system.
Which manufacturer's design to do this is the best is open to debate . What is not open to debate is the need for regular cleaning of this part of the gas operated shotgun, and attention to the correct assy of the system, along with regular inspection or changes of the barrel o-ring rubber seal. (this is a high temp rubber seal and factory replacements are not that expensive --- that's for those who want to run up to the local hardware store to find something that fits ! )
I'll speak mainly of the Remington 1100 which has been around for a long time, and is a basic gas operated gun. A few other common guns that are gas operated would be the Ithaca 51, the Browning Gold , Winchester Super X 2 , etc.
Problems with the gas operated systems in these guns are often times the cause of malfunctions that are simular in nature to the recoil operated shotguns. That is to say , failure to eject or completely eject the empty - stopping the shooting cycle. (jam)
Like with the recoil operated guns you first should understand the mechanics of the gas operated gun. In order to operate the shooting cycle the gun has a gas piston system that is acted upon by the gas pressure behind the shot/slug that is traveling down the barrel after firing. This is accomplished by having a hole or holes in the barrel that allow the gas to bleed into the gas system forward of the piston assy . When the shell goes off, the bolt is locked to the barrel and the pressure of the exploding gases drives the gas piston rearward. The piston drives the operating rods that control the bolt carrier mechanism . As the bolt and carrier travel to the rear, the bolt unlocks from the barrel ,(On gas guns this unlocking happens early in the shooting stroke) as the bolt completes its rearward travel ,it will eject the empty through the ejection port , and allows a fresh round to be fed upward into the chamber on its return forward stroke powered by the action spring.
Now to the control of this function : In order for this cycle to be smooth, and in control, the mechanism employs either a fixed or metered gas control eliment. In the case of the 1100 it is a fixed sytem so we will talk about that first. The gas hole in the barrel of the 1100 is located inside the barrel extension. The magnum barrel has a single hole and the non-magnum barrel will have a double hole. This is the only control the 1100 has for metering the amount of gas pressure used to function the shooting cycle. Since magnum loads creat more pressure, the single hole is used on magnum guns.(3 inch chambers) With the reduced pressures created by non-magnum loads, the barrels chambered for 2&3/4 inch loads uses a dual hole system to feed more gas into the system. Both magnum and non-magnum barrels will shoot a "range" of loads within the operating perameters of the gun..
So now we come to our first method of controling the function - that is the choice of ammo we use. The heavier the load - the more gas/pressure that is provided to operate the shooting cycle. If not enough gas/pressure is created to drive the piston rearward the gun will not have sufficient speed, power, or length of stroke to complete the shooting cycle. If too much gas is provided , then we are once again beating and slamming our gun to an early death - and abusing our shoulder as well.
Here again worth mentioning , when buying a used 1100 you should look for buffer damage. The buffer on the 1100 is a nylon material either black or cream colored and it is located on the rear of the bolt surrounding the back of the firing pin. They will all mush a bit but should not have cracks or chips out of the buffer. They are not hard to change out on this gun so don't let a broken one change your mind about purchase if the price is right. Let it however be a bargining chip on your side and also make you aware that the gun has likely been slamming a bit from perhaps shooting short magnums in a non-magnum gun. I have yet to see a cracked bolt on a 1100.
The gas piston & common problems : On most of the 1100's there is basically a three part gas piston and seal* . The piston sits just forward of the action bar sleeve on the outer surface of the magazine tube. It's concave surface facing forward. The piston seal which is also made of metal sits just forward of the piston, with it's convex surface toward the rear of the gun and facing the concave surface of the piston. Forward of these two parts is the barrel seal which is a special rubber type o-ring . This o-ring prevents gas from excaping the system through the front of the barrel extension. The most common problems in this system are : 1.) residue build up on the magazine tube and piston , 2.) A worn out o-ring seal. 3.) Improper assy of the gas system. I might mention here that cleaning of this system should also include cleaning the gas hole or holes in the barrel.
* Note : The later manufactured 1100's have a one part sytem that replaces the piston and the piston seal on the these guns. You can no longer buy the individual piston or piston seal from Remigton. The o-ring barrel seal remains the same.
Onward to metered gas systems : Pretty much all other gas operated shotguns I can think of have a metered gas system. (there are a couple exceptions) This system varies in design from manufacturer to manufacturer, but they all do the same thing. In an attempt to allow the gas operated shotgun to shoot a wider range of loads from light to magnum , the design of a metered gas systems uses a gas bleeding system. That is to say , they use less gas to operate the shooting cycle and "bleed" off the excess gas created by heavier loads. In the case of the 11-87 for example this is simply done by placing a bleeder hole in the barrel extension and sealing the front of this hole with a spring loaded washer . Once the pressure builds to what is needed to operate the shooting cycle the spring/washer is pushed open/away from the front of the bleeder hole, and the excess gas excapes. By doing this the gun can handle a much wider range of loads up through the magnums without developing excess pressure on the operating system.
Which manufacturer's design to do this is the best is open to debate . What is not open to debate is the need for regular cleaning of this part of the gas operated shotgun, and attention to the correct assy of the system, along with regular inspection or changes of the barrel o-ring rubber seal. (this is a high temp rubber seal and factory replacements are not that expensive --- that's for those who want to run up to the local hardware store to find something that fits ! )
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