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Old 09-28-2008, 02:55 AM   #11
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Virginian: I do not agree with you that this is a shotgun forum only. I did reread the question and the gentleman was in fact asking only about shotguns. Perhaps you meant post and not forum. Additionally I must confess that I had to look no further than my own safe at home to find a gun that gas 100% operates the action as you suggest (that's embarrassing). It is a Franchi 20 gauge that I have never even shot. It has charging bars attached to the gas piston that pushes the bolt completely to the rear. I do have a Remington 1100 but I do not have it at home, when I get to my office I will take a look to satisfy my curiosity but you are probably right about that too. I stand on everything I said about gas only opening the actions on the guns that I mentioned and every rifle that I am familiar. As for the Blish system it is strictly blow back that is retarded by a bronze saddle that fits over the bolt. As the bolt is pushed to the rear it causes the bronze saddle to have a slight interference with the body of the receiver a slows the bolt down to keep it from running away. Don't let it be said that if I am wrong I will not say I am wrong and I apologize for being snide. Now if you will please excuse me I have a nasty old crow to go eat.

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Old 09-28-2008, 01:28 PM   #12
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I have gotten to where I don't mind the crow so much myself, but damn them feathers.

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Old 09-28-2008, 06:50 PM   #13
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Virginian:

I think I may have folded my tent a little too soon on this one and those feathers were terrible. I got up this morning and took a look at my Franchi again and while it has charging bars that follow the bolt all the way to the rear, only about 3/4 inch of movement rearward movement can be controlled by gas pressure because after that the gas is released into the atmosphere and that 3/4 inch of movement only unlocks the gun. I then thought perhaps the motion of that part all initially caused only by gas moving it and its momentum (because it is heavy and a body in motion has a tendency to stay in motion) it actually worked the action, but I wasn't sure because it was starting to look more like my rifle examples where the gas only unlocks the gun. I went to my office and dug out an 1100 and it too has charging bars that are pushed initially by only gas for about 3/4 of an inch, which is the same distance required just to unlock the action and even though they follow the bolt all the way to the rear. At this point you are probably thinking pushing and I am thinking following. I then took a look at a High Standard Shadow and in my view that did it. It has everything the 1100 and Franchi has but in addition it has a piston on a 1/2 inch diameter shaft at the end of the magazine that can only move about 3/4 of an inch and it pushes on the charging bars unlocking the action but does not follow them because it is blocked by the much larger diameter magazine tube. Bottom line I think I am right, I cannot think of any gas operated gun that the gas is responsible for doing anything other than unlocking the action, then recoil takes over from there completing the cycle. I am going to call Remington in the morning and crow or no crow I will let you know. You have been a real sport about this and I wish you lived closer so we could go do some shooting.

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Old 09-28-2008, 08:25 PM   #14
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Many years ago I had the fortunate opportunity to sit next to Wayne Leek on an airplane ride, and I think I may have already asked the questions. I (surprisingly) was enough of a gentleman to make sure I wasn't driving him nuts, but he actually seemed to enjoy the conversation. I doubt he got to sit next to many gun nuts either.
On an 1100, the gas only gets the action sleeve, action bar assembly (which unlocks the bolt), and bolt moving, and then their momentum finishes the job. That's one reason why the balance of parts is so important on an 1100 - a 3" gun has a heavier sleeve and only one gas port, so that a magnum load with a longer peak gas pressure, doesn't get things moving too fast before they have to come to a sudden stop at the rear of the receiver. And they also have enough inertia that they do not unlock the bolt before the gas pressure is well past the peak. And you can tie up an 1100 so the gun does not move at all, and that takes recoil out of the picture in my view, and the action will still cycle. I actually did this years ago, proving that an 1100 really does generate less peak recoil than a pump gun. Fortunately, both stocks survived the experiment.
In thinking further about the situation myself, you may indeed be correct that some actions only have the gas unlock the bolt, and the gun already being in recoil at that point is a very necessary adjunct to their actions cycling. I do not know. I haven't really studied any other gas actions all that seriously, and I have certainly only ever completely restrained one.
I have enjoyed the conversation as well. In spite of all the drivel on the internet, occassionally I actually have the opportunity to meet someone intelligent and learn something. I wish we lived closer as well. If you ever get up this way, give me a heads up. I don't travel much anymore, but my buddies and I are going duck hunting in Canada in October to tick off one big item on our "bucket list". I got diagnosed with cancer back in March, and I think it made us all take another look at our priorities and realize that all of a sudden we may not have plenty of time for everything.

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Old 09-28-2008, 08:50 PM   #15
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Virginian:

Just my luck, I meet an intelligent and knowledgeable gentlemen that I am sure I could be friends and then he tells me he has cancer. If I might ask... I tell you what I going to try to send you a private message and my email address.

Ron

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Old 09-29-2008, 01:44 AM   #16
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Taking your brawl a bit further, with a few specific examples:

M-14 rifle gas piston "hits" the operating rod hard, but also pushes it a fair distance- 1/2 inch? That hammer-like hit imparts a high-force impact which both unlocks and drives the bolt back. Recoil effects may be present to some degree, but consider that the gas is bled to the piston just before the bullet leaves the barrel, so recoil by then is....??

M-16 impinges gas pressure on the bolt carrier "key" for a very short distance- maybe less than 1/8 inch? That "chuff" of gas-induced force is very short duration, before the gas bleeds away.

FN-FAL has an adjustable gas pressure regulator, a nice feature, if it works. I am not aware of any other common rifle having this.

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Old 09-29-2008, 03:59 AM   #17
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Quote:
Originally Posted by genie View Post
Taking your brawl a bit further, with a few specific examples:

M-14 rifle gas piston "hits" the operating rod hard, but also pushes it a fair distance- 1/2 inch? That hammer-like hit imparts a high-force impact which both unlocks and drives the bolt back. Recoil effects may be present to some degree, but consider that the gas is bled to the piston just before the bullet leaves the barrel, so recoil by then is....??

M-16 impinges gas pressure on the bolt carrier "key" for a very short distance- maybe less than 1/8 inch? That "chuff" of gas-induced force is very short duration, before the gas bleeds away.

FN-FAL has an adjustable gas pressure regulator, a nice feature, if it works. I am not aware of any other common rifle having this.
geni, welcome to the brawl but the truth of the matter I was the butthead and the Virginian was the calm head. The M14 you speak of I presume is essentially an M1 Garand with a box magazine in 7.62 NATO/308 Winchester. To answer your implied question where is recoil? Recoil started the very instant the bullet started to move and continued long after the bullet was gone. It is that recoil that continues to operate the action. You have to remember, if the rifle recoiled at the same rate of speed as the bullet, it would kill you to shoot it. However, as you know for every action there is an equal and opposite reaction. The mass of rifle absorbs this action/energy for a much longer period of time than the much lighter bullet. This can readily realized in the fact that the bolt does not travel back at the same speed of the bullet, meaning that a bullet could possibly depending on the range reach its target before the action completes its cycle. Your M16 comments I am not sure I understand so I won't comment. The FN-Fal has the feature of being able to shut the gas off to launch grenades and to work the action manually if need be. I think it has one more adjustment for blanks but I am not sure, I will look at one mine tomorrow and report back. The Styer Aug has this same feature as the FN but again I will have to check. I am fortunate enough to own these guns and while I don't have an M14 I do have a BM59 and I think one can adjust the gas on it because it has a grenade launcher. Again I will report back.

Ron
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Old 10-01-2008, 01:59 AM   #18
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genie:Well here I go again looking for another crow to eat and I haven't fully recovered from the last one. The only good thing is don't let it be said that I cannot admit when I am wrong. The M14/ BM59 has a gas piston that runs the full length of and operates the action entirely by gas. Recoil does NOT come in to play as I suggested. The FN FAL works the same way and it actually has two separate adjustments for the gas. One regulates the gas as to what ammo you are shooting and the manual says to adjust it to the proper ammo you fire the gun single shot increasing the volume of gas until the magazine holds the bolt open making it obvious that gas is the only thing operating the action. The other is to shut the gas off to operate a grenade launcher with a third position should the sytem become fouled. The Steyr Aug appears to work the same way but only has one adjuster, that has the same three positions of the FN FAL. What makes the crow even worse is that I own two Augs, one Bm59 and two FN FALs, all different configurations. I haven't even looked at them in the last two or three years and this week end I promised myself I am going to shoot them as well as some H&Ks I have. The AR 15 and SKS are like I said depending on recoil to complete the cycle. Every thing else I said about recoil, where the bullet is at while the action is functioning and time is correct.

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Old 10-07-2008, 05:47 PM   #19
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This post was so interesting that it compelled me to register.

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Originally Posted by janikphoto View Post
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?
Close, but not quite. Actions that work from the cartridge directly pushing against the bolt are known as direct blow-back actions. Most .22 LR semi autos and other rimfires fall into this category. Typically, this actions don't have locking lugs in their bolts because the bolt does not actually lock into anything. The mass of the bolt is enough to keep the breech closed temporarily until the pressure falls to safe levels. These actions work by taking advantage of mass to overcome momentum (the momentum imparted on the bolt). This is the simplest type of semi-auto action but it's not suited for high pressure cartridges.

Inertial actions are diferent. In an inertial action, the breech indeed locks and the bolt has locking lugs just like in a gas system or any other high pressure action. Inertial actions work by taking advantage of inertia, rather than just the mass of the bolt. In an inertial action, a part of the action (in the case of the Benelli system, the rear of the bolt) resists the recoil forces because it's sort of detached from the rest of the gun. Following the example of the Benelli system, as the gun moves back, the rear of the bolt wants to stay put, and a spring between the rear and front of the bolt gets compressed momentarily. As this spring loads, it reaches a point where it finally overcomes the inertia from the rear of the bolt and pushes the rear of the bolt back, unlocking the breech. It's quite an ingenious and elegant design that requires very few woking parts yet it's suitable even for high pressure systems.

It's worth mentioning that inertial guns and blow-back guns shouldn't be confused with recoil-operated guns. Recoil operated actions are yet a third and different animal. Recoil guns use recoil forces imparted on certain parts of the gun (usually the barrel and slide) to unlock the breech. Usually, the locking system is set up in such a way to delay this process mechanically by adding mass and friction to the equation (for example, by making the barrel and other parts moveable). Most semi-auto centerfire handguns use this principle, as well as some larger weapons such as the Browning 50-cal. machine gun. These guns operate on the principles of recoil and friction. These designs can be fairly complex, but can handle high pressure relatively well and are usually quite reliable.

So, to sum it up, all three systems operate through forces imparted by the recoil, but they are delayed and/or unlock the breech by the use of three very different methods:

Blow back operated systems use, mainly, mass.
Inertial operated systems use inertia.
Recoil operated systems use, mainly, friction.

Then of course there are the gas systems, which use gas, and which you've explained quite well.
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Old 10-08-2008, 01:22 AM   #20
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Quote:
Originally Posted by h2oking View Post
genie:Well here I go again looking for another crow to eat and I haven't fully recovered from the last one. The only good thing is don't let it be said that I cannot admit when I am wrong. The M14/ BM59 has a gas piston that runs the full length of and operates the action entirely by gas. Recoil does NOT come in to play as I suggested.
H2o, the M-14 I speak of is as you mentioned, the successor to Garand. The distance of gas piston movement is limited to a fraction of the entire bolt travel, so analysis by "gut instinct" is pretty difficult, but suffice to say that I believe the piston imparts a very rapid impact hit to the operating rod, which develops sufficient peak force during that instant of contact, that inertial forces then keep the rod (and bolt) moving rearward to complete the cycle. Whether any recoil force is involved is rather doubtful, since the bolt is essentially a mechanical part of the chamber until the gas piston moves the op rod, which in turn moves the bolt rearward as the locking roller "cams" upward, relieving the mechanical lock-up to the chamber. That event is happening MUCH later than when the bullet passes over the gas orifice (allowing gas flow to the piston). So, the bolt is locked until the bullet leaves the barrel, with the net result that there are then no longer any gas forces acting on the cartridge (or the bolt, therefore), to provide "equal & opposite reaction".

However, as you mention, lots of crows frequent the pasture across from my house.......
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