What is "blowback" design?

[TexasGuy]

How does it work and how is it different from any other common design?

[epsylum]

Originally posted by TexasGuy
How does it work and how is it different from any other common design?

Notice on a makarov or any bolw back auto (walther PPK SIG P232,etc.) it has only a cutout for the spent brass to exit and most bigger guns have a big squarish thing right there on the bak of the barrel?

The big honkin sqaure thing on the back of a delayed blow back barrel (as in, any browning design) is actually a timing device. It locks into place with the slide, until the pressure in the chamber drops, before unlocking and moving the slide back. Notice how nicely the barrel fits in the slide of any modern full size auto? That "snugness" is it locking into place. A blow back is very simple in that the only thing keeping the chamber closed until the pressure drops is slide weight and slide spring weight. Blow back pistols usually have wither huge slides (as in a Hi Point) or have heavy slide springs ( like a makarov).

It's simple physics really. One takes a preordained amount of pressure to unlock and move rearward, the other just plain old takes an cetain aount of pressure to move, period.

If done right the blow back design is just fine (as in a Makarov). But a delayed blow back is easier to control.

[KinderGlocken]

Let's not forget the Roller Locking Action

"Unlike the Makarov, the CZ-52 does not use a straight blowback mechanism. Because of the high power of the cartridge, the CZ-52 has a rather complicated, but strong, roller-locking mechanism. The roller lock is composed of the barrel, two rollers, and a locking cam. When at rest, the pressure of the recoil spring compresses the cam which forces the rollers outwards towards the slide.

During firing, the rearward motion releases the cam and the continued pressure will eventually push the rollers out of the detent and allow the slide to travel relative to the barrel. Therefore, the strength of the recoil spring determines when the the slide begins to move backwards.

A version of this locking mechanism is found in some modern Heckler & Koch firearms." makarov.com also in the fnfal and I believe cetme rifles.

[epsylum]

Originally posted by KinderGlocken
Let's not forget the Roller Locking Action

"Unlike the Makarov, the CZ-52 does not use a straight blowback mechanism. Because of the high power of the cartridge, the CZ-52 has a rather complicated, but strong, roller-locking mechanism. The roller lock is composed of the barrel, two rollers, and a locking cam. When at rest, the pressure of the recoil spring compresses the cam which forces the rollers outwards towards the slide.

During firing, the rearward motion releases the cam and the continued pressure will eventually push the rollers out of the detent and allow the slide to travel relative to the barrel. Therefore, the strength of the recoil spring determines when the the slide begins to move backwards.

A version of this locking mechanism is found in some modern Heckler & Koch firearms." makarov.com also in the fnfal and I believe cetme rifles.

Yeah I didn't get into that since I have (or is that "had" now?) no clue how that works.

But thanks for telling us.

[M2 Carbine]

Originally posted by TexasGuy
How does it work and how is it different from any other common design?

If you take a open ended steel pipe, put a stone in one end with a firecracker behind it, light the fuse and block that end with a piece of wood 2x4, you now have a blow back design.
The blast blows the stone out one end and knocks the 2x4 backwards.

If you have a barrel in place of the pipe and a slide in place of the 2x4 and all the machinery to operate the gun and a spring to keep returning the slide forward, you now have a blow back design pistol.

The other designs have some machinery that effectively "locks" the barrel and slide together at the instant the round is fired. Then shortly there after the barrel and slide are unlocked and the slide moves backward.

The lockup at the highest pressure allows for the use of a more powerful round and/or the use of a lighter weight slide.

[Bushbacker]

One of the best explantions and illustrations of blowback, delayed blowback and locked breech was on "Mail Call" on the History Channel of all places. Ermey explained it well with a animated sequence of each design in motion.

[RenegadeGlocker]

A blowback is a autoloading weapon that relies soley on Newton's Third law of motion (For every action there is an equal and opposite reaction) to cycle the action. No gas system, no delay, etc. The bullet goes forward, the bolt goes backward. Simple and effective.