DELAYED BLOWBACK DESIGN

[JohnHL]

The orig TSMG though not a handgun used a bronze block engaging the steel breech bolt at a slight angle. The two dis-similar materials thought to slow down the action speed as they slipped apart.,,at least slower than if the block had been made of steel like the bolt.
The idea was to create a delayed blowback action in the weapon.

Some say it's nonsense science (that principle itself).
Whatever,,the later WW2 versions of the TSMG , the M1 (M1A) were made straight blowback and w/o the complicated system. They seemed to work OK.

Ah yes, the dubious "Blish Device".

I was hoping someone would bring it up.

Thanks!

John

 

[OLDSTER]

Thanks guys for all the input. Now when our friendly debate reconvenes, I'll have more educated info. to support my side.

 

[jeffrefrig]

One of the recent NRA magazines did a review or something and explained delayed blowback and undelayed(?) blowback. Can't remember a darned thing except the delayed was easier to shoot.

 

[Walter Rego]

I believe that my AMT Automag II in .22 WMR can be considered a delayed blowback design. There are a series of tiny holes around the circumference of the chamber about halfway down. They lead into another chamber formed by a sleeve that is around the outside of the firing chamber. The idea being the brass case expands upon firing and into the holes a little bit and when pressure drops the case contracts, the grip on the chamber lessens, and the slide gets blown back to extract & eject and feed the next round.

I suppose the outer chamber around the firing chamber is to contain any gas should the case rupture and leak through the holes. You can see a series of blackened dots or dimples around the fired case corresponding to the holes in the chamber.

 

[JJEH]

H&K G3. Battle proven around the world...

 

[shocker]

I've had 2 delayed blowback pistols, both based on the Pedersen system.
PMR-30 22 WMR
R-51 9 mm +P rated
Both function reliably. The 9 mm is interesting to compare to the plethora of tilting barrel pistols.
You get a lower bore axis hence more compact pistol.
You get a slide that's easy to rack for a subcompact.

OTOH, is the extra complexity in the mechanism worth it? Probably not.

 

[s&wchad]

Delayed blowback, aka retarded blowback, is a fine design used on some of my favorite pistols. They're typically very accurate because of the fixed barrels. The downside is the internals accumulate fouling quickly and require frequent cleaning. It's a much more complex design than a gun with just a heavy slide and recoil spring.

The H&K P7's are one. They vent gasses into a chamber to slow the rearward movement of the slide, via a piston. It's basically the opposite of a gas operated semi-auto.

My other favorite is the Steyr GB. I've got three of them now; a standard model shooter, a NIB standard model and a military model. I also have two of their muzzle breaks, which are fairly scarce, reduce recoil even further and add to the "cool factor". These have internal ports and piston rings on the barrel, that vent gasses between the barrel, slide and frame to keep the action closed until pressures drop.

Please ignore the Browning GP Competition, the Kimber and the Glock...

 

[Gunhacker]

And then there is the most common delayed blow back pistol being sold today... don't forget the Hi-Point with it's beluga whale sized slide.

 

[Absalom]

Our very own S&W Model 1913 illustrates the problem with direct blowback, but in a different way:

It had not just a fixed barrel, but the entire top cover was one rigid unit. It had no slide, just a breechblock/bolt that cycled out the back of the gun.

The mass of that was so low that even the .35 Auto caliber (basically a .32 ACP) required a massively strong spring to contain the force.

So they came up with an ingenious solution: A cross-bolt that lets you disconnect the bolt from the spring and cycle it to chamber a round without any effort. This was possible because another unusual feature is that the spring is a pull-, not push action. It is located above the barrel and stretched as the recoil drives the bolt back and does its work upon contracting, the opposite of standard recoil springs.

(Not my photos, borrowed from the web)

 

[murphydog]

Have a look at the Walther CCP series, also with gas "delayed" mechanisms.

 

[colt_saa]

Started thinking about this and with the exception of my Styer GB, all of my delayed blow back firearms are HK

I am exceptionally fond of all of these

GB

P9s - 45ACP

P7

MP5/357

MP5/10

G3k

The roller delayed system that HK uses is truly amazing

The locking piece (orange) comes in about 6 different angles. These alter how long the bolt is delayed.

As an example other than firearm markings the difference between MP5s chambered for 40 S&W and MP5/s chambered in 10MM auto is the barrel and the locking piece. All other parts are interchangeable

MP5s chambered in 357 SIG or MP5/10s firing the watered down 10MM Auto ammunition use the same locking piece as the MP5/40

 

[ReloadforFun]

My understanding of the Blish Lock used in the Thompson SMG was to delay cycling. It was not needed for the gun to work and was removed from subsequent models, as mentioned above. However, it was noted that the cyclic rate increased when the Blish Lock was removed.

Currently CMMG makes a PCC using a rotary bolt. The bolt must turn to allow the bolt to cycle, forming something of a delayed blowback.

The Machine Gun Vol 4 has sections on both delayed blowback and retarded blowback. Along with other action types)

 

[dsf]

Unlocked or non-hesitation locked higher-power pistols are rare, but these do also exist. This H&K VP70 Z pistol was the first polymer-framed pistol, in 9mm Luger chambering. It was pure blowback. It relied upon the heavy slide and a stiff recoil spring to retard the slide when fired. However, because of its polymer frame, it weighed almost the same as a military 1911. It came on the market in 1970; this example was shipped in 1981.

John

I have one and have to say, kind of like it. It's too bad the trigger pull is so heavy, but it does take the firing pin spring from full at rest to fully compressed. About as safe and fool proof as one can get. The trigger can be learned so that once the long take up is through a not so bad "single action" break is had.

Rifling on the VP70 contributes to manipulating the action. It's considerably deeper than conventional rifling, causes the bullet to slow (with a resulting decrease in fps) imparting longer and greater rearward pressure on the slide.

 

[CH4]

The Rock Island Armory’s XT22 also uses delayed blow back.

 

[2152hq]

Some of the 38special W/C Target pistols built on the 1911A1 Colt that were straight blowback actions used shallow rings cut into the walls of the chamber.
IIRC Colt used the system when they factory built their pistols on the Natl Match 1911 as did a few of the custom makers.

The idea was that the case upon expanding on firing would grip those rings/grooves in the chamber momentarily and hold the action closed (delayed). Then let go and allow the action to function as a regular blowback action.
The linked-locking bbl to slide system was done away with in the guns.

Some of the custom builders (Clarke?) used the orig linked bbl locking system of the pistol in their 38specl W/C Target conversions.

 

[Nevada Ed]

There is also the 9mm High Point but I will not post a picture,

to prevent any eye damage to any of you that only enjoy looking at "Pretty" weapons.




( high standard..changed to "Point" ) sorry

 

[bc1023]

And then there is the most common delayed blow back pistol being sold today... don't forget the Hi-Point with it's beluga whale sized slide.

Hi Point is straight blowback. Granted the slide and recoil springs are heavy, but it’s straight blowback

 

[bc1023]

So all blowback pistols are delayed blowback?

Absolutely not

 

[bc1023]

There is also the 9mm High Point but I will not post a picture,

to prevent any eye damage to any of you that only enjoy looking at "Pretty" weapons.




( high standard..changed to "Point" ) sorry

The Hi Point is not delayed blowback. Its simply blowback.

 

[bc1023]

I'm not quite understanding the OP's question. They have been around over a century. Its not a difficult concept to understand.

I own quite a few delayed blowback pistols. All of mine are high end and very well made handguns. I'm a big fan of the delayed blowback.


Laugo Alien Pistol (gas delayed)








Korth PRS (roller delayed)








Benelli MP3S (lever delayed)








HK P9S (roller delayed)













HK P7 (gas delayed)























Korriphila HSP 701 (roller delayed)













AJ Ordnance Thomas (lever delayed)








Steyr GB (gas delayed)








MAB PA-15 Target (torque delayed)