We’re still working on an extended write-up on the DShK heavy machine gun, but thanks to our friend Leszek in Poland, we have some nice HD video of one firing:
The Russian counterpart to to Browning M2, the DShK uses the same flapper-locking system as the DP and RPD machine guns, and is chambered for the 12.7x108mm cartridge (9mm longer than the .50 BMG cartridge). This particular gun is the updated 38/46 version, which has the distinctive wheel-shaped muzzle brake.
And speaking of the muzzle brake, check out that flash!
Stability and recoil control on that AA tripod appear to be quite good.
The distinguishing characteristic of the M1938 versus the M1938/46 is the high-set “squirrel cage” feed mechanism on the former vis-a-vis the simplified, more streamlined feed mechanism on the latter.
As far as muzzle brakes are concerned, I’ve seen a few photographs where the late-model brakes from the M1938/46 have been fitted to the M1938. There is a pretty nice photograph of an M1938 with the original muzzle brake being fired off an AA mount during the Siege of Leningrad in C. Peter Chen’s on-line post “DShK M1938 Machine Gun / World War II Database” ( ww2db.com/weapon.php?q=66 ). The overall muzzle flash seems to be a lot less with the older muzzle brake and is mainly concentrated in a forward arc, while sideways or peripheral flash is greatly reduced. Based on that, I’m guessing the designers may have deliberately sacrificed flash attenuation for better recoil control when they introduced the new muzzle brake on the M1938/46. I also think there is a small possibility that part of the difference in muzzle flash intensity might be due to different powder types or loads in the ammunition being used.
Any other ideas about this, anyone?
Hi Earl,
that flash is vicious, it has the front legs of the tripod well illuminated in (dull) daylight.
I’m guessing that it would be a serious problem for the operator in low light conditions.
I don’t know much about the internal ballistics of the round, and what length of barrel and what operating pressure it is optimised for.
the barrel looks quite short, 36″ to 40″ at a guess, and the Soviet round had greater powder capacity that the Browning, although it may just be that a .50 cal bore allows the gas to get to the muzzel with sufficient heat remaining for it to ignite, despite a “normal” pressure-bullet travel curve.
Hi, Keith :
The DShK M1938 and M1938/46 share the same barrel length of 1070mm (42.1″) and overall length of 1625mm (64.0″). The empty (gun-only) weight is 34.0 kg (74.96 lbs.). The barrel looks shorter than it really is due to the perceived extra thickness engendered by the extensive cooling fin array.
As I understand it, the Russian 12.7mm x 108 cartridge, developed in 1934 to compete directly with the 12.7mm x 99 Browning and German 13mm Tank-Gewehr or T-Patrone cartridges, was optimized for use in a barrel of approximately that length and at an accepted chamber pressure of 360 MPa (52213 psi). The propellant used was typically 17.5-19.0 grams of smokeless Type 4/7 Tsgr powder. The extra length of the 12.7mm x 108 cartridge allows for a little more propellant capacity than the 12.7mm x 99 Browning cartridge, yet established performance figures for muzzle velocity and energy indicate that they are virtually identical even when the Browning cartridge is fired from the shorter-barreled (36″) aircraft M2 and M1921 water-cooled versions of the Browning 50-cal. HMG. The longer-barreled (45″) M2HB and water-cooled M2 deliver about 4%-6% more muzzle velocity and very slightly more (approximately 1%-2%) muzzle energy than the DShk for a mere 2.9″ additional barrel length. All this would appear to indicate that, everything else being equal, the propellant used in the Russian cartridge may be somewhat faster-burning, which, along with the inherent design of the M1938/46 muzzle brake, would result in a significant flash signature.
It should be noted that these figures are very basic comparisons using original general-purpose FMJ ball ammunition in both guns. Later developments of the two cartridges and their projectiles have since resulted in a very wide range of bullets with differing weights, muzzle velocity, muzzle energy and ballistic/terminal performance. Also, further advances in propellant compostion may have had an impact on recoil and muzzle flash characteristics, particularly in the case of the DShK.
The Wikipedia articles on the two cartridges seem to be reasonably accurate and suitable for starting a general review since both are well-established and have an extensively-known performance data base. A very good overview of the different 12.7mm x 108 rounds known to have seen service can be found at http://www.russianammo.org. For the 12.7mm x 99 Browning round, http://www.inetres.com/gp/military/infantry/mg/50_ammo.html (excerpted from Gary’s Infantry Weapons Guide) provides an equally comprehensive technical review for comparison purposes.
In the comparative examples I used in the post, I forgot to mention that the 12.7mm x 99 Browning cartridge is also rated at a slightly higher nominal pressure (378 MPa or 54800 psi) than the 12.7mm x 108.
Addition to Paragraph 2, Line 2 — The German 13mm cartridge was also known as the TuF (“Tank und Fleiger”) round.
Correction to Paragraph 2, Line 9 — Comparing original ammunition performance, the DShK actually appears to have generated a muzzle energy 7%-10% greater than the M2HB.
Good job the LAPD wasn’t using one of those in its employees’ latest spree shootings of civilians.
According to guns.ru, the barrel lengths of the following guns are:
1) DShK – 1070 mm
2) NSV-12,7 (replaced the DShK) – 1346 mm
3) Kord 12.7 (replaced the NSV) – No data, but it looks similar in length to the NSV
So, it looks like the Russians started fitting longer barrels to their newer machine guns.
Some other HMGs:
1) Browning M2HB – 1140 mm
2) Bushmaster .50 – 1150 mm
3) CIS 50MG – 1141 mm
4) Hotchkiss model 1930 – 992 mm
5) Vickers D class – 1140 mm
The Hotchkiss is 13.2mm instead of 12.7, but the cartridge case is otherwise similar so I think it is a comparable gun. The D class has a somewhat bigger cartridge, but I would still put it in the same general size class. It looks like most of the common 12.7 x 99 HMGs use a barrel that is longer than the DShK, but shorter than the NSV. The exception is the Hotchkiss (which admittedly doesn’t use the exact same cartridge).
Some Chinese HMGs:
1) Type 77 – 1016 mm
2) Type 85 – 1000 mm
3) QJZ-89 / Type 89 – 1003 mm
So, it looks like the Chinese favour shorter barrels, possibly to make the gun lighter.
I am assuming that HMGs with shorter barrels would experience increased muzzle flash for the same reason that rifles with short barrels would. Based on the above, it is possible that the amount of muzzle flash is due to the DShK’s relatively short barrel compared to many other machine guns in the same class. I haven’t compared it to any of the 12,7×81 (e.g. Vickers, etc.) or the 14.5mm or 15mm HMGs because their cartridges are too different in size to make a direct comparison.
The propellant composition would no doubt also have an effect, but I can’t think of a way to test this factor without actually testing some machine guns. That would no doubt be fun, but it’s certainly beyond my means!
As for the effect the style of muzzle brake has, it’s pretty hard to compare actual flash volume without either using a high speed camera or else capturing a lot of frames and relying on luck. The whole process happens so fast that if the flash reaches its maximum size between film (or video) frames, you won’t see the true full size. You can see this effect in videos of night firing of automatic weapons. The successive muzzle flashes will be different sizes because the frames are captured at different stages of expansion.
I’ve just looked at my post and realized that while the DShK’s barrel is a lot shorter than the NSV’s, it isn’t really much different from that of most of the others. So, scratch that entire comparison.
The only comparison that might make sense is between the DShK and the NSV, where there is quite a large difference and they both use the same cartridge.
Still a very interesting and informative article, though — thanks for sharing it!
I’ll second what Liew wrote, thanks for posting.
It’s too late tonight to start rummaging through text books for the formulae too work out the probable gas temperature at the muzzle
I suspect that it is well below the 900+ C needed for the yellow incandescence we’re seeing in the flash.
I think that what we are seeing is the powder gas burning as it mixes with air, which is where your comment about powder composition comes in.
I’m not sure about more recent Soviet and Russian powders, but Mendeleev (periodic table man) was the father of Russian smokeless powder.
French and British chemists reasoned that they would get best performance from powder with the maximum calorific value, so they plasticised the nitro cellulose with nitroglycerine, which decomposed giving excess oxygen, to react with the carbon monoxide from the nitrocellulose.
Mendeleev reasoned (correctly) that you would get more molecules for a given weight of propellant if you used straight nitro cellulose, and from the gas equations that the more molecules of gas would give you more propellant effect,
and with the happy side effect that the lower calorific value compared to powder containing nitroglycerine, would result in less barrel heating and erosion.
(he also reasoned that the physical mix of NG and NC could separate or even burn seperately, with NG burning off first – whereas “homogenous” NC could only burn the same way each time – which sounds a bit like count Tolstoy’s “happy families are all happy in the exact same way, unhappy families are each unhappy in their own unique way”)
Getting back to Muzzle flash, the essentially Co2 and water vapour from the hotter burning, stoichiometric mix of NC and NG in say “cordite” doesn’t contain anything to burn when it comes into contact with air
straight NC propellant, gives CO, which, if it is not cooled by the heat sink or venturi of a flash hider, will burn in air, if it comes out hot enough.
a complicating factor is cooling agents added to a powder, these are compounds like ammonium or sodium bicarbonate, which release gas but absorb some of the heat from the powder.
I can’t remember where I got the stuff on Mendeleev’s work. I think one of the WWi era texts up on archive.org had an English translation of one of Mendeleev’s papers. there’s a lot of good stuff from that era, when governments were anxious to get contractors interested in war work, but they still held the antiquated and short lived view that citizens could be trusted with information about guns and propellants…
Frost’s book on ammunition manufacture (published by the US NRA) is another good source
The Tolstoy quote is easy – “The Kreutzer Sonata” probably the most bitter of several short stories, each of which almost cost the Count his own unhappy marriage.
There are a couple of good re
Belated link to a .pdf of the book with the English translation of Mendeleev’s paper in it:
http://archive.org/details/powdersmokelessn00bernrich
I WANT ONE!
Was one of the lucky ones who snagged a Polish tank-mounted kit 14-odd years ago. Back then it took a bunch of us over on the Biggerhammer DShK subforum almost a year to work up a suitable (and legal!) semi-auto mod. Then, the scarcity of belts and correct mounts (aside from the Sokolovs) held many of us back from getting the full benefit of semiauto. Many of us made chamber inserts to use 50BMG as there was no way ATF was going to let 12.7 into the country. Just after I sold the kit two years later, the belts and mounts started trickling in – naturally.
[IMG]http://i28.photobucket.com/albums/c231/Brass2005/IMG_0067.jpg[/IMG]
[IMG]http://i28.photobucket.com/albums/c231/Brass2005/DShKThisisHEAVY.jpg[/IMG]
Are you planning to do it all over again? That would really be something as a project this time around, especially if the increased availability of accessories and support equipment stays consistent. I have to say that I envy you ( in a good way ), as no doubt many others on this site do, for the opportunity you had with that Polish-manufactured kit :).
Naww. Sold the property where I had a nice shooting place, so no place to safely shoot something that powerful, or have enough distance so it could really stretch its legs, so to speak. That, and IL is always trying to ban 50’s. Only parts I’ve seen for sale are bits and pieces at Sarco, and no thanks to ATF, no (useable)barrels at all. Hindsight being 20/20 I should have blueprinted the whole thing before selling it off. Still staring at an Apex Goryunov working out a plan of attack for a semi-only conversion; right next to the Polish RPD. Guess I’m getting lazy.
Thanks, Earl. Sorry to hear about the circumstances surrounding the DShK. The Goryunov project sounds really interesting, though — please let us know how it turns out when you’re ready.
One of these “reached out and touched me” at 2200′ AGL(above ground level) in an H-34 helo way back in ’67. Several rounds went right through 3/4″ laminated armor and up into the cockpit where they blew the center radio console up and through the center windscreen. The same burst hit 3 out of 5 fuel cells and started fires in all three. The rest of the flight was short and interesting. I became an instant believer in the range and power of the 12.7mm round.
Whew — Glad you’re here with us, Paul. Thanks for sharing that enlightening if somewhat harrowing experience.