Why No More Kiraly Delayed Blowbacks?


May 16, 2006, 02:11 PM
I'm very intrigued by this action, especially given the description of the Korobov TKB-517 (http://www.world.guns.ru/assault/as74-e.htm)-lighter, easier to make, more accurate, and more controllable than the AK-47, the CCCP chose the more familiar AK series anyway.

The FAMAS action uses the same basic principle, and I haven't seen any stories of any major issues with that rifle (other than that it's French.) The French obviously like the action, since the FAMAS' is based on the AAT-52 machinegun, which they've used since the 50s.

Which brings me to the question: as far as I know, every competitor in the recent SOCOM competition which brought us the FN SCAR, as well as everything mentioned as a 'possible replacement' for the M16/M4 family is gas operated, using some sort of gas piston. Why doesn't anyone try building something with a Kiraly lever-delayed blowback?

Also, anyone know where I can find a diagram of how the thing actually works, and/or more info on Kiraly's original design?

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May 16, 2006, 09:05 PM
Only person I know of who ever handled one of the commercial FAMAS semi-autos complained that it had "only one locking lug".

I dimly recall something in Ezell's last Small Arms of the World (13th edition?), but not enough to help.

Mostly just bumping this to the top, because I would like to learn about this action too.

May 16, 2006, 10:29 PM
The FAMAS, like roller-lock mechanisms, works entirely by mechanical leverage. Basically, the lever simply converts rearward movement of the bolt into an amplified movement of the bolt carrier. As an example, if the bolt were to move 1mm to the rear, the lever forces the bolt carrier to move 10mm to the rear. This greatly increases the force the bolt has to produce to get moving.

The drawbacks are, just like the roller lock, the bolt does start moving while the gases in the barrel are at peak pressure. The HK uses chamber fluting to allow some of the gas to equalize pressure on the case to facilitate moving, other makers simply polish the chamber walls really well. Either way, crud in the chamber can make the case stick, typically resulting in the case head being ripped off.

Also, since it is a purely mechanical system, any wear or slop in the parts means that the bolt will be able to move first - resulting in a similar case head ripping off.

Every system has its plusses and minuses.

May 17, 2006, 02:11 PM
My understanding is that the FAMAS also used a fluted chamber.

Popenker's site, the only place I've seen mention the TKB 517, doesn't mention how the TKB 517 stacked up against the AK in the reliability department.

It did beat the AKM in terms of accuracy, controlability, weight, and ease of manufacture though.

May 17, 2006, 06:07 PM
Well, that would explain the story I heard regarding the AAT-52.

Apparantly it is important to use lightly greased ammunition or you will rip the case heads off.

May 17, 2006, 06:42 PM
Is this the same as the CETME mechanism?

May 17, 2006, 09:58 PM
IIRC, the CETME uses a roller delayed blowback, based on the mechanism of the MG42 (still in service as the MG3). The G3/HK91 also use this type.

The basic idea is the same, just accomplished in a different manner.

Tony Williams
May 18, 2006, 02:16 AM
Not quite: the MG42 was a short-recoil design.

The roller-type retarded blowback was introduced in the Mauser StG.45 rifle at the end of WW2, then taken to Spain to be developed as the CETME, then returned to Germany to become the HK G3 rifle. HK subsequently used the mechanism in a wide variety of guns, including the MP5 SMG. However, for their current HK G36 rifle family, they adopted a piston-type gas operation instead, which should tell you something.

Tony Williams: Military gun and ammunition website (http://www.quarry.nildram.co.uk) and discussion forum (http://forums.delphiforums.com/autogun/messages/)

May 18, 2006, 01:22 PM
Oi...what the gun world needs is a 'Firearm Operating Mechanisms for Dummies' books with nice little drawings of how all of these work, exactly. The exact definitions get my head twisted up on itself at times.

Tony Williams
May 18, 2006, 07:51 PM
Well, you'll find gun mechanism descriptions in my books 'Rapid Fire' and 'Assault Rifle' :cool:

Tony Williams: Military gun and ammunition website (http://www.quarry.nildram.co.uk) and discussion forum (http://forums.delphiforums.com/autogun/messages/)

May 18, 2006, 08:13 PM
See also Hatcher's Notebook.

May 18, 2006, 10:56 PM
I've got the latter book...danged if I know exactly where it wandered off too. Haven't seen it since Christmas.

Hatcher will go on the shopping list for this weekend's gun show.

November 13, 2006, 09:17 PM
Not sure but this could be a diagram of the 'Kiraly Delayed Blowback'(KDB).

November 13, 2006, 11:25 PM
However, for their current HK G36 rifle family, they adopted a piston-type gas operation instead, which should tell you something.
Something along the lines of "our profit margin increases if we make guns out of plastic and machine the metal bits into simpler shapes"? ;)

November 14, 2006, 12:46 AM
Cool stuff...anyone read Hungarian?

Now, another question: anyone know if the French are working on a replacment for the FA-MAS, and if so, what kind of mechanism it has?

Tony Williams
November 14, 2006, 03:18 AM
Pictures of their "future soldier" types show a FAMAS, modified with a Picatinny-type rail.

Tony Williams: Military gun and ammunition website (http://www.quarry.nildram.co.uk) and discussion forum (http://forums.delphiforums.com/autogun/messages/)

November 15, 2006, 08:56 PM



Wes Janson
November 15, 2006, 09:29 PM
Does anyone have any idea where one can find a good diagram explaining the Kiraly principle of operation?

November 15, 2006, 11:46 PM
US Patent 1073908 (http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=1073908.PN.&OS=PN/1073908&RS=PN/1073908). I recommend installing Alternatiff (http://www.alternatiff.com/), then clicking the "Images" button at the top of the page.

Oh, and here's the US Patent for the FAMAS (http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=3938422.PN.&OS=PN/3938422&RS=PN/3938422). Same deal with the images.

November 16, 2006, 08:27 AM
The picture in Braith-Wafer's post is the action of the Danuvia 39M/43M submachine gun. This was the action developed by Paul de Kiraly for the Hungarian army to handle the 9mm Mauser, which was much more powerful than 9mm Para. If I recall correctly Kiraly invented this action while working for the Swiss company Neuhausen and the Neuhausen carbine (also in 9mm Mauser) was the first to use this action.

After WWII Kiraly fled to the Dominican Republic where he helped establish a small arms industry. He designed a .30 carbine shooter based on the Danuvia submachine gun called San Cristobal carbine. A 7.62 Nato version was planned but for some reason the US government did not want the Dominicans to build firearms and their factory was shut down. Small Arms Review did an article on the .30 San Cristobal awhile back.

Very interesting action, but the friction bearing surfaces on the retardation arm would probably wear out a lot faster than a gas operated gun. But probrably no big deal if you replaced that part occasionally.

December 12, 2007, 07:26 PM
This blog (http://armedcanadian.blogspot.com/) has a fantastic diagram of lever-delayed blowback:


Looks like there's a main bolt (termed bolt body or something similar), which attaches via lever to the bolt carrier, which acts as an auxiliary weight. Due to the mechanical ratios of the situation, the bolt carrier has to move a lot farther than the bolt does, which effectively increases its intertia, but without prohibitive increases in the actual mass of the system.

Wes Janson
December 13, 2007, 01:19 AM
I hate to say it, but it looks like the design would inherently cause an awful lot of wear to the rear edge of the slot milled into the receiver for the cam.

December 13, 2007, 01:38 AM
Fletchette nailed it. You need a fluted chamber to float the case, or you'll rip the case head off a high pressure cartridge. These are delayed blowback and ejection is 'brisk'

"The World's Submachineguns" has some nice photos.

The FAMAS is pretty interesting, and there a great article in the lated "Small Arms Review"

Yours truly with the FAMAS


December 13, 2007, 04:49 AM
the funny lever under the cocking handle that isn't a cocking handle(there's 2) serves as a grenade launcher sight on these things.

It's funny because you have to flip the gun sideways

December 13, 2007, 03:32 PM
Guntech! Is that a rule 3 I see there!?


Looking at it again, I suppose it isn't.

Does anyone else think that lever-delayed blowback would work wonderfully for the larger pistol calibers like .44 magnum? They don't run at pressures nearly as high as .556 NATO, the brass might be salvageable.

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