View Full Version : Blowback Vs. Recoil Operated

05-27-2006, 3:59 PM
Can anyone tell me the difference between blowback operated and recoil operated?


05-27-2006, 4:27 PM
Can anyone tell me the difference between blowback operated and recoil operated?


As far as I know, blowback and recoil operated are different terms for the NEARLY the same thing. I believe the difference is that in a "blowback" operated gun, the bolt/slide has no positive lock in the barrel or the action. The bolt is merely held closed by the mass of the bolt and the force of the spring. In a recoil operated action, the bolt must "unlock" and then be forced back by the force of the recoil. Basically, they are both powered by the same thing.

Gas operated is the different one.

05-27-2006, 5:12 PM
^ +1

a Mark II Ruger is blowback, 1911s and such are recoil operated.

05-27-2006, 5:28 PM
I'm pretty sure 1911s are delayed blowback.

I believe ohsmily has got the general idea down. I don't know for a fact as to what the definition to either are, but that is the way I have always looked at it. I don't do a whole lot of gun talk with random people, but I have only ever heard of some semi-auto shotguns (like Benelli's Enertia system) being called recoil operated. Most handguns, I thought at least, were blowback or delayed blowback. The Ruger 10/22 is a good example of a strictly blowback type of weapon, with the difference between the LR and Magnum model being a good indication of why strictly blowback firearms only exist for smaller calibers.

Of course I could very well be wrong.

05-27-2006, 5:32 PM
blowback the force from combustion acts straight onto the bolt or breach face of the weapon, it can be locked or delayed in some fashion such as in the roller locked designs or blish as in the thompson.

Recoil, the kick from the bullet being pushed forward (newtons 2nd law) operates the mechanism.

Technically they both employ newtons 2nd law but in different ways. Its so basic that its impossible to find something mechanical that dosent work using it.

In a blowback design the action begins to move the second the round is discharged. In a recoil operated mechanism everything is locked together and immobile until the bullet leaves the barrel.

05-27-2006, 6:09 PM
This is the best I could find to clearly describe the difference.

Actions, blowback vs. locked breech

Self-loading automatic pistols can be divided into "blowback" and "locked breech" categories according to their principle of operation. This classification roughly divides the operation into those specifically suitable for small-caliber versus large-caliber semi-automatic pistols.

In blowback semi-automatic pistols, typically .380 caliber (sometimes known as 9 mm Kurz, i.e., 9mm Short) or smaller, the barrel is fixed to the frame and the slide or bolt, in its foremost position, is held against the barrel only by the force of the recoil spring. The slide starts to move backwards immediately upon the gun being fired, as there is no locking action to hold the breechblock and slide locked with the barrel even temporarily.
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In contrast, in a locked breech design (typically .32 caliber or larger) the barrel is temporarily locked to the slide. The most common locked breech type is the short recoil design. In a short reciol pistol, the slide and barrel recoil together a short distance while locked together, until the cartridge-firing chamber pressure has dropped to a safe level. After sufficient travel to allow the bullet to exit and the pressure to drop, the barrel then unlocks from the slide, and the barrel's rearward motion is stopped. The ejection and loading of the new cartridge is similar to that in a blowback pistol. After the slide seats the new round into the chamber, the barrel begins to move forward with the slide, locking into place, at which point the cycle is complete.
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Gas Operated Pistol

Some cartridges, such as the .44 Magnum, are so powerful that the spring required to slow the recoiling barrel and slide becomes very difficult to compress by hand, making it very difficult for most people to load the pistol. Magnum cartridges are often found chambered in pistols which use a gas operated design, more commonly found in a rifle. One example of a gas operated pistol is the Desert Eagle.

05-27-2006, 8:32 PM
blowback means the barrel does not move.

long recoil means the barrel moves back with the bolt the length of the cartridge.

short recoil means the barrel moves back with the bolt less than the full length.

that's not exactly correct, but it's mostly right.

05-28-2006, 12:02 AM
So ive been thinking about a better way to explain this.

Blow back is like the breach face of the gun is a gas piston, gas pressure from the cartridge pushes the slide or bolt back.

Recoil is more like those swinging ball bearings where one hits a ball on one side and the ball at the end swings out. It depends on the transfer of momentum from the barrel to the slide.

05-28-2006, 1:48 AM
Think of it this way- this is easiest to understand.

A blowback gun works based on the force exerted rearwards on the case on the moment of firing- basically the gunpowder shoves the bullet forwards and the case back at the same time. A strong spring is necessary to keep the slide from moving rearwards too quickly and causing a case failure. This is also why you do not normally see calibers above .380 in blowback actions, or if so, the slide weighs a TON. Blowback pistols also seem to recoil more in the hand (because of violent slide movement).

Delayed blowback is something else altogether and is NOT a 1911 type action at all- that is wholly incorrect.
Delayed blowback works similarly to blowback, except there is some feature which keeps the slide from moving to the rear for a short time. The H&K P7M8 is delayed blowback, as the gas piston keeps the slide from unlocking until the pressure in the barrel is decreased below a set amount. The Seecamp .32 uses rings in the chamber which the case grips while under pressure to keep the slide from moving to the rear. This is delayed blowback.

Recoil-operated guns work on the inertia of the WHOLE gun on firing. If you take a Glock 19, for example, and whack it rearwards (backstrap first) into your leg hard enough, you can get it to cycle. I've done this as a demonstration- that rearwards movement, followed by your hand/arm stopping the frame, and the inertia of the slide wanting to continue rearwards is what allows the gun to function. This is NOT delayed blowback (see above).
If you were able to somehow fix the frame from moving at all under firing, a recoil operated weapon would just sit there and not cycle. I think this demostration can be done by firing a Benelli M1 shotgun against a tree trunk, or with light loads which do not transmit enough inertia to the action to cycle it.
Recoil operated guns are also more affected by limp-wristing. If you shoot with a loose wrist, you do not give the slide and frame enough differential in their inertia to cycle the action.
There is no transfer of inertia from the barrel to the slide on a modern semiauto pistol. On the old ligers/broomhandles, the slide/barrel assembly recoils together like a cannon for a short time. On a modern pistol in slow motion, you can see the action stays locked until the hand/wrist of the firer begins providing resistance to the rearward inertia (duplicated by my Glock 19 leg-slap demonstration).


05-28-2006, 9:12 AM
For those of you who are having trouble getting it and for those that think they get it, just search "Blowback" and "recoil operated" on Wikipedia.org. You can see diagrams and lengthy explanations about the specifics.

05-28-2006, 7:55 PM
Pretty much what I said, except for longer and more technical terms :D