what is the advantages/disadvantages of rifle system?


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idain
October 3, 2006, 10:09 PM
i'm a new user in this forum
i have problems with my tesis
i need helps
i would like to know bout:
1) advantages/disadvantages of
a) gas system
b) recoil system
c) blowback system

2) examples for each of them & how they work
3) what is the best system
thanks..
:)

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Geronimo45
October 3, 2006, 10:23 PM
Not too sure on the first two... I don't know if the second is really a system.
A gas system allows for lesser recoil, and longer time for the bolt of the gun to open (the time that it takes is measured in fractions of a second). That's important for bigger cartridges, so pressure drops to a safe level (somebody else can explain why).
The blowback design is usually simpler - but best for weaker cartridges. A lot of SMGs used it, since they were using pistol cartridges in things of carbine length/weight.

As for the best system - depends on your cartridge. If you've got a weaker cartridge, blowback is all you need. I think it's simpler to clean, too. Also makes for a cheaper gun, usually. That's why the little blowback pistols are cheaper than rotating lug Browning designs, too.

ctdonath
October 4, 2006, 12:02 AM
Gas operated has worked quite well in the AR15 platform.
Advantage: don't have an above-axis component (piston in comparable designs) hammering back & forth with accuracy-affecting torque.
Contention: some object to it blowing burned powder residue back into a sensitive area; others observe that is rarely a problem, especially if kept reasonably clean.
Disadvantage: I'm finding the hard way that if you put a silencer on the end of the barrel, a LOT of gas gets blown back into the shooter's face, quickly making breathing unpleasant.

MTMilitiaman
October 4, 2006, 12:27 AM
i'm a new user in this forum
i have problems with my tesis
i need helps
i would like to know bout:
1) advantages/disadvantages of
a) gas system

The gas system of operation is the most popular system found in rifles, and has seem limited use in pistols, such as in the Desert Eagle. In this method of operation, gas is diverted through a hole in the barrel, usually around the front sight block, into a gas tube. There are three main variations of this system; the long piston, short piston, and direct gas impengement. In the long piston, such as that of the Kalashnikov family, the gas is directed into a rather large gas tube, hits a large piston, which is connected directly to the bolt carrier. This sends the entire piston and bolt carrier backwards with force and has the advantage of being very simple, and very reliable. The disadvantage would be that the large amount of mass moving increases felt recoil. In short piston operation, the gas hits a gas piston which is blown back to either impact the bolt carrier assembly (FN FAL) or hit an operating rod, which hits the bolt carrier (SKS). This is more complicated but minimizes mass movement, and thus recoil. Both of these systems are more maintence free than other operating systems because the pistons tend to keep hot gases and carbon fouling restricted to the gas tube and out of the weapon's receiver. The direct gas impengment system is basically seen only in the AR-15 series. It gets rid of the gas piston all-together and simply directs gas through a narrow gas tube into a gas key, a tiny port directly in the bolt carrier, to blow it back. This makes the system very simple and very accurate, but tends to allow a lot of heat and fouling into the receiver.

b) recoil system
c) blowback system

As far as I am aware, recoil operation is basically the same as blowback. There is blowback operation and delayed recoil operation, but both operate off of recoil, or more precisely, the physic's concept of equal and opposite. Blowback operation is basically restricted to rimfires and low-powered pistols. The Ruger 10/22, Ruger Mk II, and the James Bond's .380 ACP Walter are all blowback operated. The same forces that push the bullet down the bore push backwards towards the shooter as well. This is known as recoil to us. The only reason it doesn't hit us as hard as it hits the target is the mass of the handgun or rifle is much more than that of the bullet. But this only works with relatively low powered cartridges because at peak pressure, the forces generated by the more powerful cartridges would be too violent to control. In order to control anything larger, you need to either dramatically increase the mass of slide, such as the HiPoint pistols, or create a mechanism to delay operation of the bolt or slide until pressures have dropped to a safe level. In pistols this is most often accomplished with a series of lugs and a link that holds the barrel in place until pressures are safe, then allows the barrel to tilt downwards, unlocking the lugs, and allowing the slide to travel rearward. This is seen in the 1911 Gov Model as well as the vast, vast majority of all automatic handguns you see from the Glock to the SIG, ect. The only popular recoil operated rifles that I am aware of is the HK roller locks like the G3. They control recoil with a two-peice bolt which delays through inertia the transfer of recoil forces to a series of locking ball bearings until pressures are safe. The HK series roller locks are usually very reliable and very accurate, but can have the fouling issues of the AR series. Also, even with the locking system, the action of the HK roller locks is still very violent which asside from increasing felt recoil can lead to torn case heads. HK designed a fluted chamber to remedy this, though.

As for the best system, I don't really know if there is a singular "best" system. Any of them should be evolved enough now that there are very good representatives for all of them.

Matt-man
October 4, 2006, 12:44 AM
The roller-locked HKs are usually considered delayed-blowback firearms. In a recoil-operated firearm the barrel moves rearward with the bolt for some distance. I can't think of any recoil-operated rifles offhand, just some shotguns (Browning A-5) and machine guns (Browning MGs).

A lot of pistol-caliber carbines are straight blowback designs; the Ruger PC carbines and the Marlin Camp Carbines fall into this category.

There are Wikipedia articles complete with diagrams for recoil operation (http://en.wikipedia.org/wiki/Recoil_operation) and gas operation (http://en.wikipedia.org/wiki/Gas-Operated).

I thought we had a similar discussion sometime in the past few months but I can't find the thread.

Evil Monkey
October 4, 2006, 12:56 AM
Old HK's are NOT recoil operated. They are Delayed BLOWBACK operated.

Recoil operated in a rifle is when the barrel recoils backwards to unlock the bolt. MG42 MG's were recoil operated. There was a US recoil operated rifle but it lost out to the Garand. The Steyr TMP is also recoil operated. Rifles are not built with recoil operation today because the barrel moves, thus causing problems with accuracy. Plus, recoil operation is more complex because of the moving barrel, which requires more parts.

Old HK's like the G#, HK33, and MP5 use the blowback principle but it is mechanically delayed. HK's uses rollers on the sides of the bolt that sit into to reccesses in the chamber or trunion area. Others like the French FAMAS rifle use the lever delayed blow back system which uses a lever to delay the movement of the bolt head and instead direct the bulk of energy towards the bolt carrier.

Here's some animations of mechanisms

Blowback, like the UZI.
http://www.waffeninfo.net/verschluss/bild/massezuschiessani.gif

Delayed blowback, like the HK's
http://www.waffeninfo.net/verschluss/bild/roldelboltani.gif

There was no animation but I found pics for the FAMAS lever delayed blowback
http://www.waffeninfo.net/verschluss/bild/hebel1.gif
http://www.waffeninfo.net/verschluss/bild/hebel2.gif

Here we have the rotating barrel of the recoil operated TMP
http://www.waffeninfo.net/verschluss/bild/rotbarr1.gif
http://www.waffeninfo.net/verschluss/bild/rotbarr2.gif

Animation of sks, STG44, and possibly the FAL's tiling bolt Gas operated piston system
http://www.waffeninfo.net/verschluss/bild/tiltblockani.gif

Animation of rotating bolt gas operated piston system in AK's, SIGs, nearly all belt fed machine guns, etc.
http://www.waffeninfo.net/verschluss/bild/rotboltani.gif

Take a look at this animation for the MG42. You see the rollers lock into the chamber of the barrel, but it is NOT roller DELAYED like the HK's are because the bolt gets unlocked after the barrel recoils all the way back to the furthest position to squeeze the rollers inward. It can get confusing.
http://www.waffeninfo.net/verschluss/bild/mg3boltani.gif

I love passing on good info.:D

Tony Williams
October 4, 2006, 01:33 AM
Just a technical nit-pick - those of us with an interest in bigger automatic weapons (i.e. cannon) draw a distinction between delayed and retarded blowback. Delayed blowback is used for mechanisms which are locked at the instant of firing, and then unlocked (usually by gas, but can be recoil) to allow blowback to operate. Retarded blowback refers to mechanisms which are not locked at the instant of firing, but merely have a mechanism to slow down the initial movement of the bolt.

Using that distinction, the rifles mentioned so far (FAMAS, G3) use retarded blowback. Delayed blowback weapons include the gas-unlocked 20mm Hispano of WW2 fame and several modern single-barrel, fast-firing cannon. In fact, most such guns are hybrids, because even if they are nominally gas or recoil operated, the breech opens so fast that blowback plays a major role in the process. For instance, the current Russian fighter gun (30mm GSh-301) is a single-barrel recoil-operated weapon - but it fires at 1,500-1,800 rpm, and the breech opens so fast that smoke pours out of the back and the fired cases are flung out at 100 m/s - that's faster than the muzzle velocity of a 40mm grenade launcher...

Tony Williams: Military gun and ammunition website (http://www.quarry.nildram.co.uk) and discussion forum (http://forums.delphiforums.com/autogun/messages/)

MTMilitiaman
October 4, 2006, 02:22 AM
Hmm, learn something new everyday, I suppose.

So what would be the difference between a recoil operated firearm, and Benelli's inertial operation?

Tony Williams
October 4, 2006, 02:56 AM
I'm not familiar with the Benelli system. Can you describe it?

Tony Williams: Military gun and ammunition website (http://www.quarry.nildram.co.uk) and discussion forum (http://forums.delphiforums.com/autogun/messages/)

Matt-man
October 4, 2006, 04:17 AM
The Benelli system uses a two-piece bolt. The bolt body is separated from the bolt head by a spring that Benelli calls the "inertia spring." When the gun recoils rearward, the heavy bolt body tries to stay put (inertia - a body at rest tends to stay at rest) and compresses the spring. Note that it's moving forward with respect to the rest of the gun during this process. As the gun reaches the end of its recoil, the spring pushes the bolt body back towards the rear of the gun, starting a relatively conventional extraction/ejection/loading cycle powered by another spring at the back of the gun.

It almost seems like a delayed blowback system (the bolt head rotates to lock/unlock), though I don't think that's true. I think they stay locked long enough that there's little blowback pressure left by the time they unlock. I understand that the guns won't cycle if they don't move enough under recoil, which leads me to think that most of the energy used to cycle the gun comes from the bolt body compressing the inertia spring and not from blowback. From what I've read this issue is the reason why the USMC's new Benellis are gas-operated.

MTMilitiaman, I'll describe how my recoil-operated Browning A-5 works so you can get an idea of the differences. In the A-5, the barrel and bolt both move rearward under recoil. They move together all the way back to the bolt-locked-back position (this being a "long recoil" design). The bolt stays locked back while the barrel moves forward powered by the recoil spring at the front of the gun. As the barrel moves forward the bolt is still hanging on to the shell, so it extracts & ejects the empty. When the barrel has moved sufficiently forward the bolt is released to move forward and chamber another round, powered by the operating spring in the buttstock.

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