How weight effects cycling

[lbsrdi 1,078]

Obviously one would like to have their gun to be lightweight. My question is how does weight of the Saiga12 affect the guns ability to cycle and eject/feed ammo. I am not a physics expert, but would assume that it has to have some effect one way or the other. Any thoughts? Would two identical guns cycle differently if one was twice the weight?

[gunfun 3,931]

The only way I could see that mattering is due to a limpwristing issue. I do not thing that is relevant for a properly functioning saiga 12. I have tried to make mine miss feed by holding it loosely at the waist with weak ammo. No problems. you aren't going to get it much lighter than factory without making it an 8" SBS, so if it feeds your weakest ammo while holding it loosely, you should be good. If it works, it works.

 

I think the weight is mostly an issue for blowback firearms. I have S&W target .22 that is the special heavy target version of that particular model. It has a heavier barrel and slide to add stability. The thing is, it has a reputation for being less reliable than the standard version, because the mass of the slide is too much for soft shooting target ammo to overcome. This is pretty much the opposite of the problem you are concerned about.

[KC913 324]

You would have no issues weather you stripped the Saiga 12 down to nothing or added 20 pounds of junk to it. As long as you securely shoulder the weapon it will cycle. The only thing that would impede this is if you let the weapon move rearward and absorb the recoil. ie; limpwristing, firing from the hip, etc.

[lbsrdi 1,078]

I was thinking that the heavier gun would cycle easier. I could be way off, just a question I have been thinking about for a while.

[KC913 324]

The only reason it would cycle easier would be the obvious difference in weight would result in less felt recoil for the shooter. But same principles apply.

[lbsrdi 1,078]

Ok, so no change in the action inside of the gun, just a change in the felt recoil?

[L5K 162]

It should have no effect at all. The weapon is gas operated. The same amount of gas goes through the ports whether the gun is mounted solidly, or whether it is somehow suspended loosely in midair. The pressure inside the barrel is what cycles the weapon and this pressure is the same (given the same load) no matter what is physically happening around the weapon.

[KC913 324]

Yeah, pretty much. Kind of like going from a polymer frame pistol to a heavy steel frame. But there isn't much you will add to a Saiga 12 that will noticeably reduce felt recoil.

[KC913 324]

It should have no effect at all. The weapon is gas operated. The same amount of gas goes through the ports whether the gun is mounted solidly, or whether it is somehow suspended loosely in midair. The pressure inside the barrel is what cycles the weapon and this pressure is the same (given the same load) no matter what is physically happening around the weapon.

 

If the weapon was suspended in mid-air, it would result in the gas hitting the piston, causing the entire rifle to move rearward and not allowing it to cycle properly. The weapon has to be somewhat stable for the bolt to properly cycle.

Edited February 5, 2011 by KC913

[1mile50 102]

It should have no effect at all. The weapon is gas operated. The same amount of gas goes through the ports whether the gun is mounted solidly, or whether it is somehow suspended loosely in midair. The pressure inside the barrel is what cycles the weapon and this pressure is the same (given the same load) no matter what is physically happening around the weapon.

 

If the weapon was suspended in mid-air, it would result in the gas hitting the piston, causing the entire rifle to move rearward and not allowing it to cycle properly. The weapon has to be somewhat stable for the bolt to properly cycle.

 

The gas would "hit" the piston tappet face and all inside exposed surfaces of the tappet cylinder, including the backside of the selector plug, the same way no matter how the weapon was supported. The pressure would still increase and the tappet would unlock the bolt and the chamber gases would the cycle the bolt just the same way.

What I wonder about is if the feed would be compromised by a loosely supported weapon.

Edited February 5, 2011 by 1mile50

[corbin 621]

So long as the weapon is held firmly, the weight shouldn't really matter. The only way I could see it mattering is in the weight of the carrier. Adding a super huge handle off the side or something like that could affect things.

[The_Caged_Bird 474]

WRONG! If the weapon is truly functioning properly, you could fire it and it would function no matter how you hold/not hold the weapon. It is not blow-back operated, it is gas operated.

 

I've experimented with the way I hold mine since I opened up the ports. It doesn't matter, IF the weapon is functioning properly. If you have to shoulder the weapon hard or put the butt-stock up against a tree, your gun is NOT functioning properly (Mike D, this wasn't aimed at you, we know that you were doing that to test the strength of the front feed-lip of your drum). There is a big difference between functioning and functioning properly...

 

I will say though, that I shoulder the weapon hard to try to be nice to my shoulder, but it doesn't affect my shotgun's performance one bit.

[raleighsaiga 81]

 

If the weapon was suspended in mid-air, it would result in the gas hitting the piston, causing the entire rifle to move rearward and not allowing it to cycle properly. The weapon has to be somewhat stable for the bolt to properly cycle.

 

Nope. Gas pressure pushes equally in all directions, and the only thing that can relieve the rise in pressure from firing is for the piston to cycle.

 

Now, even "gas operated" firearms are not immune to the effect of recoil forces, but a properly functioning and tuned gas-operated firearm should not be sensitive to how tightly it is held.

[MikeD 541]

WRONG! If the weapon is truly functioning properly, you could fire it and it would function no matter how you hold/not hold the weapon. It is not blow-back operated, it is gas operated.

 

I've experimented with the way I hold mine since I opened up the ports. It doesn't matter, IF the weapon is functioning properly. If you have to shoulder the weapon hard or put the butt-stock up against a tree, your gun is NOT functioning properly (Mike D, this wasn't aimed at you, we know that you were doing that to test the strength of the front feed-lip of your drum). There is a big difference between functioning and functioning properly...

 

I will say though, that I shoulder the weapon hard to try to be nice to my shoulder, but it doesn't affect my shotgun's performance one bit.

Hey, let's get this straight. I put it against the tree because I'm a big puss. No, I put it against the tree to reduce the forces on the front mag catch. All of those videos of me firing off of a tree was with prototype mags of greatly reduced strength compared to production mags. I did it to keep them from coming apart and breaking, even then it didn't prevent it all the time.

 

The rest of this isn't pointed at you either but just some answers on the question.

 

Weight does matter. First, how a gun is held will affect the function of the gun regardless if it is gas operated. In theory if the gun was able to recoil at the same speed of the bolt carrier all of the energy of the gas would be for nothing. The bolt carrier wouldn't even move rearward from it's position because the rearward moving gun would move with it at the same speed. This is in theory and the saiga-12 doesn't kick that hard even if it was floating in air completely unsupported. I know we say a loosely held gun causes energy loss but really that is a bad way to state it. There is energy loss of cycling potential but all the energy is still there, it is just cancelled out but the movement of the platform holding the mech.

 

Next, over all weight of the gun, assuming all moving internal parts are the same weight... If your gun weights 30 pounds vs 10 pounds it isn't going to change a thing if the gun is completely stable with zero rearward movement possible. But that isn't how we shoot these things, they do kick. So with that into account a 30 pound gun is going to kick less than a 10 pound gun and there for less of your cycling energy of the carrier will be lost (canceled out). It takes more energy to get a 30 lb object moving than a 10 lb object. But it is not practical to weight down a gun to account for a weak running system and I am sure that some of these guns would still have problems even if you eliminated all recoil movement of the receiver.

 

Weight of the moving parts; bolt carrier, bolt, etc... Changing the weight of the mechanical parts is going to change things. But this is where it gets really tricky with a gillion variables to consider and I won't be going into them all and my human brain can likely only calculate partially without exploding... If you add much weight to the carrier you are going to make more energy required to move it. If you remove weight you are going to reduce the energy required to move it. This can have varying effects. It might take more energy to move a 30 lb object than a 10 lb object but this doesn't necessarily mean reduced weight is good. The carrier is only pushed for a very short stroke. The rest of it's movement is dependent on the transferred energy to it (kinetic energy, inertia). A moving 30 lb object is going to carry a hell of a lot more energy than a 10 lb object moving at the same speed. If you reduce the weight of the carrier will it have enough of this stored energy to finish the cycle against the springs? If you increase the weight of the carrier will it get enough energy to get it moving? It is a delicate balance. I will say this though and please note before hand that I am in no way tied to Ohio Rapid Fire, but when they were working on their galil project this is what the found... The galil charging handle knob... They made some to put on the carriers... They first tried to make these solid without hollowing out the knob... Their guns were failing to eject. They hollowed out the knob and the ejection issue was solved. If you know the size of the knob you know that the amount of material removed to hollow it out is very minimal... In this instance the minimal added weight was enough to make or break the cycling. It is my GUESS that adding weight to the carrier is not ideal and will hurt the cycling some unless you are going to compensate it with increased gas flow or something. It would be easy to test adding weight buy removing the cover and clamping varying weights to the carrier. It would also be easy to test reducing weight to the carrier but might not be as easy to undo this test... I am not recommending anyone try this. It is on our list of test to preform but just haven't got around to it yet...

[Nailbomb 10,221]

A lighter weapon in general will in effect transfer the power of the recoil to you faster, a heavier weapon will be more sluggish to move and transfer it over a wider period of time. In effect dampening the effect.

 

Changing the weight or friction on the internal parts or moving assembly will also have a effect as a lighter or well polished assembly will cycle more readily.

 

I saw one thread on here where a gentleman machined a section of the bolt carrier the lighten it in a competition gun. It was rather interesting.

[corbin 621]

Well explained, Mike.

[lbsrdi 1,078]

So a heavier Saiga(ie.attachments) theoretically would hip fire better than a lighter gun, even if the difference may not be noticable in a well tuned gun?

[L5K 162]

A lighter weapon in general will in effect transfer the power of the recoil to you faster, a heavier weapon will be more sluggish to move and transfer it over a wider period of time. In effect dampening the effect.

 

Changing the weight or friction on the internal parts or moving assembly will also have a effect as a lighter or well polished assembly will cycle more readily.

 

I saw one thread on here where a gentleman machined a section of the bolt carrier the lighten it in a competition gun. It was rather interesting.

 

Exactly true, changing the weight and friction on the INTERNAL parts will help cycling. Overall weight of the rifle, not at all. Effectively, the gas pressure inside the barrel creates a bomb. The expansion of the pressure pushes out equally in every direction. The pressure pushing on your barrel, bolt face and the load are all equal. The bolt is locked in place with lugs, it cannot back up. The barrel is well made and does not give, so the load moves down the barrel. Once the load passes the gas port, this pressure begins to press on the gas piston. The gas piston is connected to the carrier which is not at all anchored to anything except a spring pressing it forward, so it also begins to move back, compressing the spring. Once the gas piston clears the gas block, pressure is lost on that end (because of the "flutes" in the gas tube, but the carrier is already moving backwards, and continues to do so because of inertia. In moving backwards it spins the bolt out of it's lugs, allowing it to also move backwards with the carrier and then it stops and the spring returns the entire system to battery. The only variables in this system are the weight and power of the load, the weight of the internals and the power of the springs. Yes, recoil will press backwards on the entire weapon, but that has no effect on the pressures that are still building inside the weapon and cycling it.

 

The only effect a heavier Saiga would have on actual firing is the recoil on the shooter. A heavier weapon would probably be easier to hip fire because there will be less recoil on the operator due to the weight absorbing the recoil.

[MikeD 541]

So a heavier Saiga(ie.attachments) theoretically would hip fire better than a lighter gun, even if the difference may not be noticable in a well tuned gun?

100% without a doubt... The heavier weight would mean the kick would be less and would cancel out less of the carrier motion.

[Paulyski 2,227]

Does this thread originate from a weapon with a quad rail?

 

Some have experienced, I believe with a Halo(?) the quad rail, the way it clamped to the gun may have been effecting cycling.

 

That being said, one can shoot a properly tuned S-12 1 handed & limp-wristing in my experience.

Only boarderline guns need to be braced firmly.

[MikeD 541]

 

Exactly true, changing the weight and friction on the INTERNAL parts will help cycling. Overall weight of the rifle, not at all. Effectively, the gas pressure inside the barrel creates a bomb. The expansion of the pressure pushes out equally in every direction. The pressure pushing on your barrel, bolt face and the load are all equal. The bolt is locked in place with lugs, it cannot back up. The barrel is well made and does not give, so the load moves down the barrel. Once the load passes the gas port, this pressure begins to press on the gas piston. The gas piston is connected to the carrier which is not at all anchored to anything except a spring pressing it forward, so it also begins to move back, compressing the spring. Once the gas piston clears the gas block, pressure is lost on that end (because of the "flutes" in the gas tube, but the carrier is already moving backwards, and continues to do so because of inertia. In moving backwards it spins the bolt out of it's lugs, allowing it to also move backwards with the carrier and then it stops and the spring returns the entire system to battery. The only variables in this system are the weight and power of the load, the weight of the internals and the power of the springs. Yes, recoil will press backwards on the entire weapon, but that has no effect on the pressures that are still building inside the weapon and cycling it.

 

The only effect a heavier Saiga would have on actual firing is the recoil on the shooter. A heavier weapon would probably be easier to hip fire because there will be less recoil on the operator due to the weight absorbing the recoil.

The over all weight of the gun will have an effect. The only way it wouldn't is if the gun was mounted in a way that zero movement of the receiver occured when firing.

 

Also lightening the carrier... It might help up to a point to lighten. But there is going to be a point that if it is too light it won't have the stored kenetic energy to complete the action. In theory, if the bolt carrier weighed zero (impossible) as soon as it lost the pressure it's rearward movement would stop and the springs would close it back up.

 

Also the saiga-12 is different than AK rifles. The piston on a rifle is basically an operating rod on the shotguns. The is a puck in the shotguns that pushes what would be the piston in a rifle. In the shotgun the piston only moves about 1/2" and is stopped in the gas block. This short stroke is enough to transfer the energy to the bolt carrier. The shotguns have a different system because the surface area of what is the piston in a rifle is not enough area for the pressure to act on. There for the shotguns have a independent piston of a larger diameter. This larger diameter increases the ft pounds of force from the pressure in the chamber.

 

Also, it is a very common misconception that the pressure is contantly building in the barrel until the projectile leaves the barrel. I believe this misconception comes from the fact that the projectile's velocity is (usually) increasing the whole way down the barrel. Let me give an example. This example might not be exact but will be close, I don't have my notes in front of me... Take a 1903 Springfield firing a 30.06 round for example. At the instance of ignition the pressure is right at 50,000 psi. Once the projectile is about 10 inches down the barrel the pressure has dropped to about 25,000 psi. At around 16 inches down the barrel the pressure is now about 10,000 psi. I can't remember what the velocity of the projectile is at these points but it is increasing even though the pressure is decreasing... This is also why the breach of most guns are thicker than the rest of the barrel and a good reason for thick heavy trunnions in more modern guns. This is also one way the V-Plug slightly increases the cycling power with low brass. The V-Plug reduces the size of the gas chamber. The reduced gas chamber volume means it takes less gas to pressurize the chamber and it happens faster. If the chamber pressurizes faster it is at the same time able to pressurize at a high PSI because the projectile isn't as far down the barrel.

[termite 463]

Mike,

Is there any data as to what the pressures are, say "at the muzzle", just as the bullet exits the barrel. I don't believe it's as great as some of the Insteins that I have talked to have said. You are correct in the stated pressures of a said caliber is measured at the chamber, but I wonder about at the muzzle.

[lbsrdi 1,078]

Paulski,

Although I do have a quad rail mounted (Chaos) this thread originated simply by a theory I have been thinking about. I just assumed that the extra weight would slightly keep the gun from moving rearword as much as it would with a lighter gun, therefore keeping more energy in the movement of the carrier. My gun cycles flawlessly in part because of your input. Thanks to all who share their knowledge on this forum.

[The_Caged_Bird 474]

Well, I never intended that that weight of the gun didn't affect the perceived recoil. I did, however, intend to say that it doesn't matter how any human being holds the weapon, if it's functioning properly, it will cycle the way that it should.

 

Thanks for the knowledge, Mike, I appreciate you expounding on your knowledge of the Saiga-12 platform as you know far more than I. I'm just using the knowledge I've gained from experience with one gun. I might not be right all of the time but I AM right about MY gun, which doesn't care how I hold it. It still functions as it needs to when I fire it from the hip...

[MikeD 541]

Well, I never intended that that weight of the gun didn't affect the perceived recoil. I did, however, intend to say that it doesn't matter how any human being holds the weapon, if it's functioning properly, it will cycle the way that it should.

 

Thanks for the knowledge, Mike, I appreciate you expounding on your knowledge of the Saiga-12 platform as you know far more than I. I'm just using the knowledge I've gained from experience with one gun. I might not be right all of the time but I AM right about MY gun, which doesn't care how I hold it. It still functions as it needs to when I fire it from the hip...

I couldn't agree more. I don't consider a gun reliable if I have to watch how I hold it.

[MikeD 541]

Mike,

Is there any data as to what the pressures are, say "at the muzzle", just as the bullet exits the barrel. I don't believe it's as great as some of the Insteins that I have talked to have said. You are correct in the stated pressures of a said caliber is measured at the chamber, but I wonder about at the muzzle.

I am diggin it up now. I'll post solid number (correct myself above) including the velocities in a bit.

[pedal2alloy 206]

There have been cases where adding attachments has affected cycling. One example is the quad rail and there are other examples on other rifle platforms. But it's more complicated than just the added weight of the attachment. Sometimes an attachment can change the harmonics of the shock wave and how it is dissipated through the rifle.

[MikeD 541]

Regarding the 1903...

 

Barrel length is 24", projectile starts around 2.3" in the barrel already...

 

Projectile, PSI (roughly), feet per second (roughly)

at 3" 45,000 775

3.5" 49,000(peak) 1050

7.5" 25,000 1825

10" 18,500 2125

17" 10,000 2475

20" 8,500 2625

24" 7,000 2700

 

From ignition to exit is 0.00098 seconds!

You can see the velocity start leveling off quickly. I am not sure at what point velocity would start to decrease as well, given a longer barrel.

[MikeD 541]

There have been cases where adding attachments has affected cycling. One example is the quad rail and there are other examples on other rifle platforms. But it's more complicated than just the added weight of the attachment. Sometimes an attachment can change the harmonics of the shock wave and how it is dissipated through the rifle.

Yes, there are so many factor and variables it could melt a brain. But sometimes I think new items get the blame sometimes when really it might be it was run hard and put away wet. The someone might get something new, strap it on and have some problems... The plastic fowling in these shotguns set when they cool. I can't see harmonics being much of a factor with the shotguns as a high power rifle. The shock wave is low pressure in comparison. Some of the hottest 12ga rounds are around 12,000 PSI in comparison to the rifle round above.

[G O B 3,516]

Regarding the 1903...

 

Barrel length is 24", projectile starts around 2.3" in the barrel already...

 

Projectile, PSI (roughly), feet per second (roughly)

at 3" 45,000 775

3.5" 49,000(peak) 1050

7.5" 25,000 1825

10" 18,500 2125

17" 10,000 2475

20" 8,500 2625

24" 7,000 2700

 

From ignition to exit is 0.00098 seconds!

You can see the velocity start leveling off quickly. I am not sure at what point velocity would start to decrease as well, given a longer barrel.

 

 

Velocity will increase until the friction of the bullet against the barrel exceeds the force of the expanding gases against the back of the bullet.