Fluted Barrels???

H

hube1236

New member
Okay, I am looking into rifle purchase from strictly Handguns because of a TFL'er in Madison Wisc named Skip. It looks like I am going to spend a lot of friggin' money I don't have. Oh well, $3000 now, $75 in grocery coupons when I have to turn them in at gun point (HI MR FBI and CARNIVORE MAN).

When discussing rifles, one may hear the terms, blow back, delayed blow back, gas operated, mechanical roll back (?). I also hear the words fluted barrels. Could someone explain (in a Reader's digest way) what these terms mean?

Also, if anybody has an FAL Style- .308 they would like to give me in exchange for a good feeling in their heart, I will pay for postage.
 
Fluted Barrel: A barrel with longitudinal grooves to reduce weight while maintaining stiffness, and to possibly improve cooling during long strings of fire. The diameter of the barrel is greater than the standard sporter-weight barrel. The archives here contain quite a bit of discussion of the pros and cons.

Blowback: The rearward force on the cartridge-case actuates the self-loading mechanism.

Delayed Blowback: Like the Colt 1911, some sort of linkage very briefly slows the actuation of the self-loading mechanism.

Mechanical roll-back: I don't know.

Gas operated: Like the Garand. A small hole in the barrel near the muzzle lets some of the powder gases drive the operating rod rearward, cycling the action. A piston-and-cylinder deal, like a car engine, but just a straight push.

Hope this helps,

Art
 
Well, let's see.

In reference to an automatic or semi-auto firearm, we need to understand that the breech has to remain closed for a short time after the gun is fired. If it does not, the pressure in the fired cartridge will burst the cartridge case and harm the gun, shooter, or both.

Blowback means that the breech is kept closed only by the inertia of the breechblock. This is the simplest system and in low powered guns (.22 LR, .25 ACP, .32 ACP, .380 ACP) it is adequate.

Delayed blowback is the same except that there is some kind of delaying device, like a cam that the breechblock has to push out of the way. Delayed blowback is not very common.

All FA/SA firearms are gas operated in the sense that the gas from the burning powder not only expels the projectile but also directly or indirectly works the reloading mechanism.

Specifically, the term gas operation refers to a system having a gas port or trap in or on the barrel which channels a portion of the gas to a piston or similar mechanism to operate the breech block. The M1 rifle, M1 carbine, and M16 are gas operated. This mechanism is usually designed so that the bullet has left the barrel and the pressure dropped off before the breech is opened.

Recoil operation does not use the gas pressure directly, but operates from the recoil caused by the motion of the projectile. Here, too, the system is designed so that pressure drops to a safe level before the breech opens. Since the system depends on recoil, if the barrel is blocked so the projectile can't move, the gun will not operate. Some recoil operated guns are the M1911, the Glock, the Browning Auto 5 shotgun, and the old Johnson rifle.

I have not heard the term "mechanical rollback", so I will have to pass on that one.

As for fluted barrels, they are simply barrels with lengthways cuts to create a barrel with (for example) a section in the shape of a cross rather than in the shape of a circle. This is a way to retain barrel stiffness (which helps accuracy) while cutting weight. A one-inch diameter barrel with flutes will be almost as stiff as a solid cylinder one-inch barrel, but will be a lot lighter. Most flutes are cut between the breech and the muzzle so that both ends are circular.

HTH

Jim
 
Were you asking about HK & CETME's delayed blowback, roller locked system?

Here's the simplified version from www.hkpro.com :

roller1.jpg


and

roller2.jpg
 
Hey, Jim! If the only thing holding the breech of a Blowback system in place is inertia and spring pressure, why would it not cycle when a barrel is plugged? Plugged or no, there is indeed a force acting to the rear.

Think about the typical .22 rifle, or a Grease Gun or Sten...

The inertia-factor affects WHEN the cycle occurs; the spring affects HOW FAST the cycle occurs. I submit that the cycle will occur.

After all, I've had a 1911 cycle when only the primer--now powder charge--pushed the bullet halfway up the barrel. I fail to see how a plug directly in front of the bullet would make any difference.

:), Art
 
Hi, Art,

I guess I wasn't too clear. There is no locking mechanism in a blowback system, only the inertia of the breechblock. If the bullet does not move, the gas pressure forces the breechblock to the rear and does so very forcibly, since there is no opportunity for the pressure to drop. The case will almost always burst and there will usually be damage to the gun.

The 1911 pistol is a locked breech, recoil operated system, not a delayed blowback. In a recoil operated mechanism, the bullet must move to set the recoil mechanism in motion. Otherwise, the barrel and slide remain locked together. The gas is pushing in all directions equally and if the bullet can't move, the barrel can't move, so the slide can't move. The name is correct; the 1911, Luger, P.38, Glock, etc. are truly recoil operated.

In the case of a no-powder (primer only) load, the force of the primer can move the bullet enough that there is some recoil and movement of the slide in relation to the barrel. But note that the bullet did move.

In most cases, a no powder load will leave a bullet in the barrel and will not fully cycle a normal pistol. But guns set up with a light slide and light spring for pure target will almost always cycle. If the bullet has not exited, the result will be a bulged barrel if the next round is fired.

There is another interesting facet to most SMGs, and that is something called Advanced Primer Ignition, or API. When the bolt closes in one of those guns, a fixed firing pin (STEN, M3, Thompson M1A1) or a driven firing pin (MP38/40 or other Thompsons) strikes the primer slightly before full bolt closure. This means that the blowback force has to overcome not only the inertial mass of the breechblock but also the remaining forward momentum. That is what allows the breechblock to be lighter or have a lighter spring than would be the case if the breechblock were fully at rest before firing. This is why the open bolt versions of the TSMG are easy to operate*, while the semi-auto closed bolt versions take three men and two small boys to cock.

*The original Model 1927 semi-auto is an open bolt gun.

Jim
 
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