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Shotguns "R" us

pros and cons to intertia driven systems and gas blowback systems

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Hey, I'm lookin at 12 ga autoloaders, and was wondering....... whats the difference between gas operated systems and inertia operated systems?!?! I think i kinda know how they work, but what i really want to know which is better and what are good and bad about them. If anybody knows please help me out here.:D

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Inertia is operated by inertia and gas by gas lol....

Inertia like the benelli ARMI system use the force of the shell and a spring that compresses. Gas systems cycle the gases through small holes in the barell...Inertia cycles faster and there is less to clean, Gas guns are a ***** to clean.I think one disadvantage of inertia I beleived if the gun isnt shouldered tight it may jam. Someone correct me if im wrong.

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From what i have heard, on inertia models you can't mount much stuff on one or it won't work properly. As for gas, i have heard nothing like that. Want to mount stuff on a Tactical AutoLoader? Get a Gas.

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In the Benelli inertia system

(1) the shell is fired and recoil begins,

(2) the gun backs up in recoil

(3) while heavy bolt carrier, due to its inertia,

remains momentarily in place.

(4) The bolt head is locked into the barrel by a rotating cam recoils with the gun, and backs into the momentarily motionless bolt carrier.

(5) This action compresses a heavy spring between the bolt and the bolt carrier.

(6) When the bolt carrier begins to move the compressed spring propels it backwards towards the butt of the shotgun,

(7) The bolt carrier compresses the recoil spring,

(8) while extracting and ejecting the fired shell

(9) then the recoil spring sends the bolt carrier and bolt forward again,

(10) lifting the next shell into position to be fed into the chamber,

(12) their inertia drive the new shell fully into the chamber and the bolt head stops moving forward

(13)the bolt carrier body continuing forward, due to its remaining inertia, rotates the bolt about its long axis by the cam, turning the locking lugs into engagement with the barrel/barrel extension.

 

I forgot to mention that the hammer was cocked and the trigger reset during the extraction, ejection part of this movie.

 

Too much weight on the gun, which has to move sharply to compress the spring between the bolt and the bolt carrier, retard the velocity enough to prevent the heavy spring to be compressed sufficiently to store enough energy to propel it back and do all that I described above after the compression.

 

Does this describe it well?

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Nice job, Michael!

My understanding is that anything that retards or stops the gun from moving backwards will impede the inertia system so, if you put the butt against a concrete wall (I've never done this) and fire it, the action will not cycle. Conversely, if you hold it away from your body, (I have done this) it will cycle just fine. So, adding weight might impede the cycling but "limp shouldering" will not.

The M4 is gas-operated out of USMC's concerns that all their add-ons might prevent an inertia action from cycling.

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Well, since Michael stated the interial system so eloquently, I'll try to do the same for the gas operated semi-auto's.

 

1. The shell is fired and the shot/wad cup head on down the barrel.

 

2. As the wad gets to about the end of the forearm, where there is a small hole, or port (sometimes multiple) in the barrel. This is open to the "cylinder" that is integral to the barrel. This is a polished cylinder with an o-ring at the muzzle end that seals the gases from moving forward (towards the muzzle end.) The cylinder also acts to hold the barrel in the receiver when you tighten down the magazine tube cap.

 

3. Inside the cylinder there is a piston ring that seals the annular area between the magazine tube and the cylinder walls. The piston ring is sometimes a two-piece arrangement, sometimes one piece.

 

4. The expanding gases from the powder being burned that are pushing the shot/wad out the barrel then also act to push the piston rings rearward along the magazine tube towards the receiver. The cylinder is only an inch or an inch and a half long, and as soon as the piston rings pass beyond the cylinder, all the gases are vented to the inside of the forearm (which is why you'll often see vents in the forearm of gas-operated semi-autos.

 

5. The "action sleeve" is a metal cylinder that slides up and down along the outside of the magazine tube that is connected to action bars which are connected to the bolt, much like the slide on a pump gun. When the gun is "in battery" the action sleeve is tight against the piston rings. The movement of the piston rings acts on the action sleeve and pushes it towards the receiver very much like the action in a pump gun. This rearward movement unlocks the bolt from the breech, and allows the bolt to move rearward, ejecting the spent hull.

 

6. The action spring (in some guns this spring is in the stock, in some it is on the outside of the magazine tube between the receiver and the action sleeve) pushes the action assembly and bolt forward into battery, again, an awful lot like a pump gun behaves.

 

In simplest terms, a gas-operated semi-auto acts a lot like a pump gun, but instead of your arm providing the motive force to cycle the action, it is gases from inside the barrel pushing a set of piston rings which then moves the action rearward, and a spring returns the action forward.

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Inertia

 

Pros:

  • Clean and simple - few moving parts and no carbon build-up as gasses are not routed through the system
  • Reliable under varying conditions - a properly cleaned and maintained Inertia system will typically cycle more rounds without a hiccup than will a gas system.
  • Lightweight - Fewer parts means less weight
  • Shorter forearms - Since there is no gas system pistons, rings, etc., the forearm on an Inertia gun can be made shorter.

Cons:

  • May not cycle light loads - Benelli makes it quite clear that their systems are not designed to handle the lower recoils generated by light trap and field loads. These loads simply do not create enough energy to cleanly cycle the system.
  • Possible failure due to improper operation - Users can shoot loads near the minimal range and still have problems if the gun is not shouldered properly. There is also the possibility of a failure due to not having the bolt fully closed and rotated. This typically occurs when the user has tried to "ease" a round into the chamber without making much noise, such as when setting up on a close gobbler.
  • Possible failure due to bumping and handling - Because the bolt does not "lock-up", a firm bump on the butt of the gun may allow the bolt to back up just enough to create a light primer strike and misfire. Seasoned Benelli shooters on the move learn to give the bolt a visual check and a firm bump when there's a break in the birds flying.
  • Less recoil reduction - An Inertia gun delivers the full amount of the discharged shell's energy back into the stock. Inertia works on recoil energy, and there is no gas system to vent any discharge energies into a piston. The shooter can add mercury recoil reducers or other recoil scrubbing devices to help with the heavy loads, but again these devices may raise the minimum load that the gun will cycle, due to the added weight.

Gas

 

Pros:

  • Reliable and versatile - A gas system can be metered or adjusted to cycle anything from the lightest loads to the heaviest. As long as the system stays clean, it will perform.
  • Inherently less recoil - The system routes some of the discharge gases back into the piston to cycle the action. Since this energy never makes it to the muzzle, recoil is reduced in a manner similar to porting.

Cons:

  • More cleaning - A gas system is subject to require more cleaning. The discharge gases and unburnt powder are routed through the barrel ports and into the piston and rings. With each firing, more carbon and impurities are introduced into the mechanics that cycle the gun.
  • More parts - More parts to clean. More parts to break. More parts to lose.
  • Heavier - The gas system adds weight. While it helps with recoil, it's not welcomed on a long hike through a swamp or a grain field.

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Inertia guns do not necessarily fire faster. Currently the Winchester/FN system is the fastest IIRC.

 

The INertia system kicks harder and is more load sensetive, but is also simpler, more durable, and MUCH cleaner (unless we are talking about the ARGO system, which is pretty dang clean).

 

Inertia is more sensetive to the way you hold the gun as well. Hold the buttstock of a benelli inertia gun against a wall and fire it, and it will not cycle.

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In the Benelli inertia system

(1) the shell is fired and recoil begins,

(2) the gun backs up in recoil

(3) while heavy bolt carrier, due to its inertia,

remains momentarily in place.

(4) The bolt head is locked into the barrel by a rotating cam recoils with the gun, and backs into the momentarily motionless bolt carrier.

(5) This action compresses a heavy spring between the bolt and the bolt carrier.

(6) When the bolt carrier begins to move the compressed spring propels it backwards towards the butt of the shotgun,

(7) The bolt carrier compresses the recoil spring,

(8) while extracting and ejecting the fired shell

(9) then the recoil spring sends the bolt carrier and bolt forward again,

(10) lifting the next shell into position to be fed into the chamber,

(12) their inertia drive the new shell fully into the chamber and the bolt head stops moving forward

(13)the bolt carrier body continuing forward, due to its remaining inertia, rotates the bolt about its long axis by the cam, turning the locking lugs into engagement with the barrel/barrel extension.

 

I forgot to mention that the hammer was cocked and the trigger reset during the extraction, ejection part of this movie.

 

Too much weight on the gun, which has to move sharply to compress the spring between the bolt and the bolt carrier, retard the velocity enough to prevent the heavy spring to be compressed sufficiently to store enough energy to propel it back and do all that I described above after the compression.

 

Does this describe it well?

Just a bit

anyway, do you know what is good about this compared to a gas or whats good about a gas compared to this iif you do please lemme know thanks

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thanks for all the responses, I'm looking into autoloaders especially the cz 712 and the stoeger 2000, since one is gas and one is inertia im trying to find out as much as possible

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Tucker's response is very clear and generally accurate.

 

One exception to the "heavy" rule for gas guns. I won a Tri-Star Viper at a Pheasants Forever banquet. Its a gas-operated semi-auto.

 

Lightest gun I own.

 

Kicks like a freaking mule, even with target loads.

 

Looking forward to hunting pheasants with it this fall, since its so light and easy to carry.

 

But, so far, so good. I've shot a few hundred shells through it, and its only failed to cycle (didn't fully eject the spent hull) a few times.

 

Would I have bought this gun myself? no. But free is good.

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thanks for all the responses, I'm looking into autoloaders especially the cz 712 and the stoeger 2000, since one is gas and one is inertia im trying to find out as much as possible

 

The Stoeger is a proven gamble.

I haven't heard much about the CZ one way or the other.

The best reviews I've heard on the $400 class semi-auto have been on the Baikal MP153/Remington SPR453 (same gun - different labeling)

 

I actually have a MP153 that I bought last year and have yet to fire it.

I might take it to the dove field on Monday just to give it a try.

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The Stoeger is a proven gamble.

I haven't heard much about the CZ one way or the other.

The best reviews I've heard on the $400 class semi-auto have been on the Baikal MP153/Remington SPR453 (same gun - different labeling)

 

I actually have a MP153 that I bought last year and have yet to fire it.

I might take it to the dove field on Monday just to give it a try.

 

You have heard good things about the spr453?

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From what i have heard, on inertia models you can't mount much stuff on one or it won't work properly. As for gas, i have heard nothing like that. Want to mount stuff on a Tactical AutoLoader? Get a Gas.

 

Are you talking about flashlights? I dont see what else you would mount on a shotty besides maybe ghost sights but i dont see what that has to do with the operation of the bolt (gas or inertia).

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If you increase the gun weight on an ID gun, you slow the recoil speed; that doesn't allow the inertia spring to compress fully and you get cycling problems. Not an issue with a gas gun which cycles by gas pressure alone.

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The only con I can think of with inertia guns is related to the pro I like about gas guns.

 

Inertia guns tend to be underbored. Many gas guns are overbored.

 

With lead, I find little difference.

 

With steel shot, I find that overbored barrels tend to throw better patterns than underbored barrels, especially with larger steel shot.

 

This is why I shoot several Benellis and several gas autos.

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my 2 cents. i prefer the long recoil guns, ie Franchi AL-48, Browning A-5.but a like the smoothness of the gas op guns a little better as far as comfort.my Charles Daly is a lot softer to shoot than the Franchi is. that AL-48 packs a whallop...on both ends.

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If you increase the gun weight on an ID gun, you slow the recoil speed; that doesn't allow the inertia spring to compress fully and you get cycling problems. Not an issue with a gas gun which cycles by gas pressure alone.

 

This is what i am talking about NJgunner... And no i didn't say just flashlights, Just stuff in general.

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thanks for all the responses, I'm looking into autoloaders especially the cz 712 and the stoeger 2000, since one is gas and one is inertia im trying to find out as much as possible

solution... buy both:D

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As the owner of an M-2, I am fascinated by the "fact" that the inertia system will not function properly if the gun is fired when held up against a concrete wall. Is this a "rumor", or has anyone actually tried it? And could someone please explain to me why this matters to anyone, and give me any reasonable scenario of when I might need to know this "failure" of the inertia system?

 

A curious person wants to know!

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I've never tried the concrete wall test, but I have seen my SBEII fail with lighter loads when fired from the hip.

The closest one can get to the brick wall scenario in the field is to attempt a shot at 180 degrees (straight up). In this case, the skeletal structure aligns in such a way that there will be little to no give when the gun is fired.

 

I have seen Inertia guns stovepipe in such cases.

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Just a bit

anyway, do you know what is good about this compared to a gas or whats good about a gas compared to this iif you do please lemme know thanks

 

The ARGO system is roughly the inertia system + 2 gas pistons that will cycle the BCG if the weapon somehow does not have enough "recoil" to cycle normally, aka too heavy, shot loosely, etc.

 

At least I think that's how it works.

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