Krinkov Brake and PDC
Can anybody please provide some details about a Krinkov Brake?
I know what it does or at least claims to do. I do not know how it does that.
The question is,
how?
Thanks!
Thank you all who responded.
I did some research on the Krinkov Brake and here is what I found.
Krinkov Brake is a gas expansion chamber attached to the end of the muzzle to allow for complete combustion and expansion of the bullet propellant charge. It is most useful in short barrelled Kalashnikovs, like the AK-74U pictured below:
Thus, even if the barrel is a 16" barrel or a 8" barrel, the bullet will come out with the same muzzle velocity. This works especially well for AK-74, but in an AR-15, shortening the barrel will result in a drop in muzzle velocity because all the propellant does not get enough opportunity to burn up and hence has less pressure to push the bullet out.
A similar attempt was made by OFB-RFI with the INSAS short barrelled version. To compensate for the short barrel, they added an expansion chamber. The 5.56 cartridge used in the INSAS packs a lot of punch and AFAIK, was cited to be too powerful for a short barrelled gun. The PDC or expansion chamber was probably done to ensure the bullet does not lose its punch and at the same time to prevent too much muzzle flash.
PDC: Pre-Discharge Chamber
There has been enough speculation about the short cylinder under the barrel of the Kalantak'07, highlighted in red boxes in the two images below:
Name: It is called the PDC or Pre-Discharge Chamber.
Operation: When the bullet passes the gas-outlet on top, some of the gas goes into the gas-pipe on the top of the barrel and pushes the piston back. Now, the bullet travels further forward and part of the remaining expanding gas gets into the PDC under the barrel and expands (and cools down due to Joule-Thompson effect). As the bullet exits the barrel, there is a sudden reduction in pressure at the barrel end and the the gas inside the PDC is sucked out.
Purpose: Reduction of the temperature, and consequently, the flash of the exhaust gas following discharge of the bullet from the barrel; the flash being otherwise extremely noticeable in short barreled firearms.
Patent: Yes. Owned by OFB.
Source: My 'friend', a junior employee at RFI today asked his 'sir' and actually met one of the scientists who perfected this device.
The added bonus is that the expansion chamber prevents a lot of the propellant from burning off outside the barrel, and thus doubles up as a flash suppressor. Of course, the conical end of the Krinkov Brake also helps in that regard.
The photo there reminded me that with the type shown at the bottom, the amount of dust and dirt (or snow) thrown up while firing from the prone position is reduced. Avoids revealing the firer's position too much.
The two pieces at the bottom (in the quote above) are not exactly meant to offer expansion. The one with the oblique cutaway actually sits on the muzzle facing top-right (from the rifleman's position) and directs more of the expanding gas in the top-right position to compensates for the top-right 'jump' that typical Kalashnikovs experience. As the rifle, on firing, tends to move to the top-right position, the reaction from the top-right ejecting gas compensates for that with a bottom-left push. This increases stability. The other piece has bi-directional ejection and is probably meant to encourage gas to move in two opposing directions, thus providing no lateral movement and so that part of the backward reactive force is reduced and this is probably one reason why AK-74 has much less recoil than an AK-47.
W.r.t. the latest picture that was quoted, if the bottom-right muzzle accessory was installed in a way that one of the two cutaways were facing downwards, it would still throw up a lot of dust. The bottom-left oblique cutaway tends to face upwards in most installed AKs, but is not exactly upwards, but top-left facing. Therefore, while it definitely helps prevent the rifle throwing up dust when fired from a prone position, its main function is to increase stability.
Notice in the image below, how the oblique cutaway is not facing exactly upwards but facing top-right (from the operator's perspective) or top-left (from the camera's perspective):