Delayed blowback

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Blast

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How much more pop does delayed blowback, aka, short recoil, impart to the bullet? Does bullet leave barrel before breach opens? What exactly are the advantages over standard blowback?




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Always use two hands with pistols...one in each:cool:
 
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(quote)How much more pop does delayed blowback, aka, short recoil, impart to the bullit? Does bullit leave barrel before breach opens? What exactly are the advantages over standard blowback?


No pop is imparted to the bullet.The bullet is the pop,so to speak.
Yes the bullet is long gone from the barrel if the gun is working properly.
Delayed blowback,short recoil ect..is the way the gun safely discharges the excess energy from the combustion of the powder charge before allowing the breach to open and cycle the slide,along with the recoil spring.Straight blowback pistols were fine when the rounds of the day were small..22,.25,.32,.380.These cartridges can only produce so much energy to cycle the mechinism.Once the higher powered 9mm and 45acp rounds became available a new system was needed,ala delayed or short recoil systems. Hope this helps a little!
 
Thanks Berettaman, it do help. but what I meant by "pop" was power. If all of the power is concentrated on propelling the bullet from the barrel before any is lost through breach, that should translate into increased fps. I was just wondering by how much; 20, 50, 100, etc.. And about 9mm needed a new system, my Hi-Point carbine is 9mm and standard blowback; and I believe there are quite a few 9mm's that are standard blowback. I don't know a whole about .45's.
 
In both delayed blowback and traditional recoil systems, the slide, or slide and barrel, begin moving immediately. This lowers pressure in the blowback and increases barrel friction of the recoil guns. Either way, it's a wash. A certain amount of energy is subtracted from the bullet to cycle the weapon in either case.

Delayed blowback's advantage is not velocity. It's accuracy and reliability. The fixed barrel provides both and is proof against failures to extract and double feeds. They are also generally a 1/2" shorter per barrel length compared to a recoil gun.

HK P9S
HK P7
Steyr GB
Benelli B76 B80
Heritage Stealth
Vector CP-1
 
Actually delayed blowback, as well as locked breech designs, are used when the power of the cartridge is too much to allow for reasonable sized springs and slide mass. Either design is more complex than straight blowback, and of course, more expensive to manufacture.
 
Hate to be a stickler, but just for the record, delayed blowback and short recoil are two different things. The distinction doesn't really matter to the answers already given, but like I said, just for the record, they aren't the same thing.
 
A "blowback" action has nothing that locks the barrel to the breech face. They are held together by the spring force. A ruger 10/22 rifle has a blockback action. So does a Makarov, most .22LR pistols, and a fair number of .380-class pistols.

When the round is fired, there is obviously force from the expanding gasses pushing back on the cartridge case, and onward onto the bolt face. The inertia of the bolt itself and the spring force resist this rearward force long enough for the bullet to leave the barrel and pressure to fall to acceptible levels. In other words, the bolt moves rearward slowly enough that the bullet has left by the time that it is far enough back that, had the bullet not left, there would be too much pressure. Thus there must be a certain maximum ratio of cartridge "power" (or imparted momentum) to the inertia of the slide, and the spring strength.

This is why you can have a direct-blowback submachine gun in .45ACP (the HK UMC), but not a direct-blowback .45ACT pistol-- the pistol's slide (the "bolt") is not massive enough.

In delayed-blowback pistols, the separation of the barrel from the bolt face is delayed by some other mechanism. As someone else pointed out, this allows higher power (pressure) rounds to be fired without pelting you with brass shards as the case explodes, which would happen if the breech face separated from the barrel when the pressure was too high, like having WAY too much headspace.

All Glocks besides the .380 (which are not imported to the US anyway) are delayed blowback. For the first 1/8" or so of rearward travel, the barrel and the slide are still LOCKED TOGETHER. This means that the case cannot move backward - the breech face is held in position. Once past the 1/8" mark, you'll notice that the barrel is pulled down allowing the slide to move to the rear, ejecting the round.

The HK P7 uses the high-pressure gasses from a port in the barrel to hold the action CLOSED until that pressure has dropped to a level appropriate for ejection.

-z
 
Thanks all for the info, I am enlightened.
Well, don 't stop now Higgins, what is the distinction between the two? I'm still learning.:D


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Always use two hands with pistols...one in each:cool:
 
In the first place, we should know why the concern about locking the breech for a high pressure round. If we fire, say, a .45 ACP from a blowback pistol of normal slide weight, the breech will open before pressure drops and the case will burst, damaging the gun or the shooter. Keeping pressure in to increase bullet velocity has little to do with it.

The only thing really holding the breech closed in a blowback system is the mass of the breechblock. The spring adds a little to the mass, but can slow the slide, as in the Astra pistols, the old S&W's and the like. Normally, it serves to return the breechblock to battery. Blowback guns have been made without a return spring; they worked fine. In a blowback system, the breechblock begins to move as soon as pressure builds, but the mass is great and breech opening is delayed by inertia.

In a recoil operated system, like the Model 1911, the Luger, or the Browning auto shotguns, the barrel and slide are locked together and the barrel-slide combination is moved by recoil, not gas pressure itself. The gas pressure does not open the action; the whole idea is to keep it from doing so. In other words, if the projectile does not move, the gun does not operate. Period.

The difference between short recoil and long recoil is that short recoil unlocks the barrel from the breechblock as the combination moves backward. In long recoil, the combination goes fully to the rear and then the barrel is unlocked to come forward, followed by the breechblock. The Browning A-5 and its clones are long recoil operated; the only pistols (AFAIK) to use the system were the Hungarian Frommers.

There have been blowback pistols made that use high power ammo. The Spanish Astra company made a series in 9mm Largo and in 9mm Parabellum, and the Hi Point pistols are blowback. The Astras used a fairly heavy slide, a heavy spring to slow the breechblock and a little trick with the hammer that made them effectively delayed blowback. The Hi Point uses a very heavy slide.

SMGs not only have a fairly heavy breechblock, but also make use of something called advanced primer ignition. That means that the primer is fired by a stud in the bolt so ignition begins as the bolt is still moving forward. Powder ignition is so rapid that the building pressure has to fight not only the weight but also the inertia of the still forward moving breechblock which increases the mass resisting the backward pressure.

Jim
 
As I understand it, the Glocks are locked breech, recoil operated, as are 1911s, BHPs, SigSauers, etc. The P7 is delayed blowback, its gas cylinder is not positively holding the slide shut, it is acting as an additional spring against opening. Handy listed some other delayed blowbacks, to which I would add the 1905 Mannlicher and the Remington 51 and 53. But some sources put the Remington-Pedersen design in a class all its own, and one writer included the Benelli 76 with them. There is some debate as to whether the Savage autos are locked breech with rotating barrel, or delayed blowback with only 5 degrees rotation. The rotating barrel MAB type R is definitely delayed blowback, the PA15 firmed it up to a locked breech. Kimble .30 carbine pistols and Colt .38 Special Gold Cups with moving barrels but no locking engagement are delayed blowback, the Colt with very little delay. The Mann pocket pistols, Seecamp .32, and High Standard 9mm T3 have chamber rings that act to delay blowback by letting the brass expand into the ring.

Advanced primer ignition pretty much requires open bolt operation, but is not limited to submachine guns. Consider the Oerlikon 20mm anti-aircraft gun, the Navy crews called it "spring operated."
 
Jim nailed it...a blowback design uses the mass of the slide to take the pressure and the spring to return it and another round to battery.
A delayed blowback design can be "delayed" by many means.
A Makarov Ultra was delayed by "texturing" the inside of the chamber..as the shell expanded under its own pressure it would "grab" the walls of the chamber and resist being stripped by the extrator/slide temporarily...thus the delay.
Gas delays are not really common and work in a couple of different mechanical/pneumatic designs. Most work on the same theory, the pressure created by the round is transfered to the breech by a piston or other mech/pneu force, until it the bullet leaves the barrel... with no bullet in the barrel anymore, pressure drops and all trapped gas/pressure is released and so is the slide.
There are smaller blowback designed 9mm guns out there..not just the massive Hi Point...Accutech is one...good design I believe just not very good quality.
And Glocks are a locked breech design..just like most other guns that are present design s/auto.
Shoot well
 
Unless the MAB is greatly different than other rotating barrel designs (Beretta Cougar), it is also short recoil. The barrel travels back briefly with slide, rotating out of lock up as it travels.

Short recoil can use a rotating lock as above, a tilting barrel lock (1911, Glock) or a seperate mechanism to lock (Beretta 92, P38, CZ52, MG3 machinegun, etc.) If the barrel moves any distance to the rear at all, it is short recoil.
 
Blast, no need to reiterate difference between short recoil and delayed blowback. I think it has been covered above adequately already.

Handy, If I understand correctly, I do believe the MAB PA-15 is delayed blowback, not a recoil design. The MAB's barrel turns in place and is not allowed to move rearward - just like the Savage pistols.

Now, here's a stumper for everyone out there - how does the FN Five-SeveN operate? If anyone can answer that question for me, I'd be grateful and amazed. FN wouldn't tell me because it's a LEO/Milit weapon, and, well, I'm neither. Supposedly it's a totally unique (new) delayed blowback method developed by FN.

Anybody know anything about the FN Five-SeveN? Help.
 
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