Jump to content


Photo
- - - - -

Forgotten Weapons: The MKB-42(w)


  • Please log in to reply
16 replies to this topic

#1 MikeRex

MikeRex

    Member

  • Members
  • PipPipPipPip
  • 82 posts

Posted 05 February 2011 - 01:40 PM

MKb42(W) | Forgotten Weapons


Interesting link with disassembly views of the Walther response to the MKB-42 program. This is the one that did not become the STG-44.

The outward appearance is quintessentially German. It's a pressed-steel design with the charging handle on the left side. The innards... are a mess; I'm not entirely sure what to make of them.

The design is gas operated, though I can't quite figure out the annular piston. Locking is by a rotating bolt that looks similar to the Lewis gun's or the FG-42 (cam surfaces on the bolt, not on the carrier like most subsequent designs) and a lot of little parts I can't make heads or tails of.

The handguard reminds me a bit of the Mauser STG-45.
  • Gebirgsjaeger likes this

#2 sf_cwo2

sf_cwo2

    Member

  • Members
  • PipPipPipPipPip
  • 191 posts

Posted 21 March 2011 - 07:43 AM

Once it was shown the MKb42 H did not need to use an open bolt, the fire control parts of the 42 W were adapted to the new MP43-series weapons.

#3 MikeRex

MikeRex

    Member

  • Members
  • PipPipPipPip
  • 82 posts

Posted 23 March 2011 - 06:02 PM

Oh hey, look at that.

They do look rather similar.

Did the Germans have a phobia about closed-bolt operation of automatic small arms or something? The FG-42 fired open-bolt for full auto too.

#4 sf_cwo2

sf_cwo2

    Member

  • Members
  • PipPipPipPipPip
  • 191 posts

Posted 29 March 2011 - 08:20 PM

Oh hey, look at that.

They do look rather similar.

Did the Germans have a phobia about closed-bolt operation of automatic small arms or something? The FG-42 fired open-bolt for full auto too.


Initially, they thought 7.92 k would quickly heat the barrels to cook-off temps. The few MKb42 (W)s tested showed that closed-bolt full-auto was possible with the round. However, the FG42 definitley needed open-bolt-- it fired full-sized 7.92 through a light barrel.

#5 MikeRex

MikeRex

    Member

  • Members
  • PipPipPipPip
  • 82 posts

Posted 30 March 2011 - 01:28 AM

I'm not so sure. All their 7.92mm aircraft guns like the MG81 were closed-bolt. Granted, the M4 carbine has a fairly thick barrel, but the videos I've seen show people putting about seven magazines through back to back full auto to get a single cook off at the end. Getting an ammo cook off with a magazine-fed weapon isn't that easy.

#6 MikeRex

MikeRex

    Member

  • Members
  • PipPipPipPip
  • 82 posts

Posted 31 March 2011 - 11:51 PM

Found that video:

YouTube - Colt M4/AR-15 Fired Full Auto untill it catches on fire

It's 14 magazines back to back full auto before cookoff occurs. That's 420 rounds at which point the carbine is ON FIRE.

I think the Germans overestimated the facility of magazine-fed weapons to cook off.

#7 marc780

marc780

    Member

  • Members
  • PipPipPipPipPipPip
  • 585 posts

Posted 14 April 2011 - 07:04 PM

Small arms designers have never solved the cook-off problem. The early machine guns like the Vickers, were water-cooled. This worked, but the water in the barrel jacket was subject to freezing, and the jacket was subject to bullets and other forms of damage. it also made the gun too heavy to move rapidly, which is exactly what a fast-moving mechanized army spends a lot of time doing.

The open bolt concept is designed so that a round is never left in the chamber for more then the instant of firing. Anybody who's fired a semi auto knows how fast they heat up, barrel temperature (exterior) can reach 750 degrees F quickly and in battle conditions, barrels often glow red hot. I knew a guy who was in Vietnam and he told me about defending his perimeter one time against an NVA night attack. He said the barrel of his M-16 got red hot from all the firing and the end simply bent over and wilted like a tulip! (There are no range breaks on the battlefield of course, you shoot what you got as long as you can!)

There is a "product improved" M-60 that someone makes that has a "super-barrel" made of special alloys including stellite, a machine gun equipped with this barrel can be seen in tests firing several hundred rounds with no interruption, no barrel damage and no misfires (i think it is on youtube under M-60).

#8 muscogeemike

muscogeemike

    Member

  • Members
  • PipPipPipPipPip
  • 175 posts

Posted 15 April 2011 - 12:44 AM

There is a TV program called "Sons of Guns" they develope a water cooling system for two M-16's and mount them side by side with a 200 round mag. It works but I'm not sure why they went to all this trouble and money. Arn't there a number of 5.56 mm light mg's already around?

#9 MikeRex

MikeRex

    Member

  • Members
  • PipPipPipPip
  • 82 posts

Posted 19 April 2011 - 08:07 PM

Bore damage from heat and cookoff are two separate problems. M2 heavy machine guns, of late, also sport stellite liners and those fire from a closed bolt.

Considerable improvements could be achieved by simply using a heavier profile barrel to give it more thermal mass, but apparently carrying around around spare thermal mass in the form of spare barrels is preferable.

There are other solutions, like the high-ignition propellant developed by Dynamit-Nobel for the caseless G11 rifle, but again, I suspect that cook-off simply isn't a big problem for personal weapons. Note that in the test video it requires fourteen magazines back to back to get the M4 carbine to cook off. That's substantially more than soldiers generally carry in combat.

And again, the synchronized MGs in fighter aircraft cowlings were all closed-bolt and seemed to get away with it just fine. Consider that cook-offs in such a mounting would have been disastrous as it would have caused continuous fire that bypassed the interrupter gear and would likely damage the propeller. I'm unaware of any special design features in such guns for better sustained fire except maybe the propeller slipstream.

#10 sf_cwo2

sf_cwo2

    Member

  • Members
  • PipPipPipPipPip
  • 191 posts

Posted 11 July 2011 - 08:08 PM

I'm not so sure. All their 7.92mm aircraft guns like the MG81 were closed-bolt. Granted, the M4 carbine has a fairly thick barrel, but the videos I've seen show people putting about seven magazines through back to back full auto to get a single cook off at the end. Getting an ammo cook off with a magazine-fed weapon isn't that easy.


I am sure, that's why I typed it. If you'd read Sturmgewehr!-From Firepower to Striking Power you would have been better informed. The HEER ordered tests on closed-bolt prototypes to verify the safety of such. Aircraft guns had the benefit of 200+mph breeze flowing over the barrel to cool it. Now, comparing today's weapons to WW2 weapons (or older) is pure folly. People once thought the Earth was flat. Showing a pic from the Hubble telescope doesn't change that fact. I guess you could dig up an old corpse and show them the pic and see what happens.

#11 sf_cwo2

sf_cwo2

    Member

  • Members
  • PipPipPipPipPip
  • 191 posts

Posted 11 July 2011 - 08:18 PM

There is a "product improved" M-60 that someone makes that has a "super-barrel" made of special alloys including stellite, a machine gun equipped with this barrel can be seen in tests firing several hundred rounds with no interruption, no barrel damage and no misfires (i think it is on youtube under M-60).


The '60 has always had Stellite-liners in its barrels. I believe the liner was only in the first 1/3-1/2 of the barrel (starting at the chamber) so maybe this new one is fully-lined. You can get the Pig so hot as to actually follow a bullet down the barrel by the bulge it creates as it travels to the muzzle. At this point, the barrel is totally trashed.

#12 sf_cwo2

sf_cwo2

    Member

  • Members
  • PipPipPipPipPip
  • 191 posts

Posted 11 July 2011 - 08:35 PM

There are other solutions, like the high-ignition propellant developed by Dynamit-Nobel for the caseless G11 rifle, but again, I suspect that cook-off simply isn't a big problem for personal weapons. Note that in the test video it requires fourteen magazines back to back to get the M4 carbine to cook off. That's substantially more than soldiers generally carry in combat.


The G11 was far from perfected. Aside from the fall of the East, the G11 was about to be shelved because the ammo caused excessive barrel erosion. However, it used a rotating breech cylinder & chamber to avoid a cook-off by feeding ammo 90 degrees from bore axis. Straight down was an opening called the unloading port. That allowed airflow to cool the barrel. It was a neat system and I wish it was made available to the public for purchase.

I believe we covered cook-offs in another thread so I'll leave a few brief facts...
Weapons have two stated rates of fire: theoretical/cyclic and actual rate of fire.
Colt's data for the M4/M4A1 is as follows-
cyclic 700-1000 RPM
semi 45-65 RPM (including time for mag changes)
auto/3RB 150-200 RPM
sustained (meaning you'll be engaging targets frequently for an extended period of time) 12-15 RPM

Compare with the open bolt, full-auto only LMG (Model 750):
cyclic 600-800 RPM
auto 150-200 RPM
sustained 65 RPM

Edited by sf_cwo2, 12 July 2011 - 08:44 AM.


#13 sf_cwo2

sf_cwo2

    Member

  • Members
  • PipPipPipPipPip
  • 191 posts

Posted 12 July 2011 - 08:54 AM

For some reason I'm having problems posting replies here. Let's try this...
The primary reason for caseless ammo in the G11 was not to avoid cook-off. It was the only way to accurately deliver a 3RB at over 2000RPM.

#14 MikeRex

MikeRex

    Member

  • Members
  • PipPipPipPip
  • 82 posts

Posted 15 July 2011 - 06:23 PM

I'm aware that the G11 wasn't designed with caseless ammo to resists cookoffs. Indeed, if one were trying to resist cookoffs, starting with a caseless design would probably be the worst possible starting point. Rather it was the special denatured RDX-based propellant, which had a higher autoignition point than conventional nitrocellulose-based propellants that allowed it to resist cookoffs even without the extra thermal mass of a brass case to protect the propellant and to remove chamber heat during the ejection cycle.

Speaking of conventional nitrocellulose-based propellants, both the 5.56 NATO and the 7.92K used them. The powder chemistry has changed somewhat; mostly the addition of burn-rate modifiers, flash suppressants and other additives, but the energy density of the propellant is almost exactly the same as it was sixty or even eighty years ago. Barrel metallurgy has improved somewhat as well, mostly in terms of the consistency of the material, toughness, wear-resistance and the addition of a hard chrome lining, but the heat capacity of a kilogram of barrel steel is almost exactly the same as it was sixty five years ago.

Going even further, my reloading data books show that the 7.92K and 5.56 NATO have very nearly the same powder weight in typical loads; about 25 grains for 125 and 62 grain projectiles respectively. Estimating the cookoff propensity of an STG-44 by approximation with an M4 is thus imminently reasonable.

Also interesting to note is that a number of small-arms field guides will tell you that the closed-bolt MP5 is more prone to cookoff than other SMGs. Really? The weight I find for a standard MP5 barrel is 9 ounces and 28 ounces for an M4 barrel. Standard 9mm loads have about 8 grains of powder, so that's about a third the thermal load per shot and about a third the thermal mass, proportionately more surface area (but air-cooling rates are pretty trivial compared to the maximum practical ROF, or so says my engineering guide to small arms).... and I'm skeptical that anyone has ever actually managed to achieve a cookoff in an MP5 using using anything like a standard duty load of ammo.

I strongly suspect that open-bolt firing was just a design convention for submachine guns by the 40s, and fear of cookoff was just a convenient rationalization. Indeed, with the exception of the Reising SMG I can't think of a single closed-bolt SMG design in WWII. It wasn't simply a matter of design simplicity either; there were several SMGs that had articulated firing pins and still fired from an open bolt. The Winchester self-loading series of rifles, which was well known and had even been partially militarized by the French had existed before there were any submachine guns, and showed that closed-bolt, hammer-fired blowback carbines were entirely mechanically sound. What's more, they used a telescoped bolt, and it wasn't until WWII was over that anyone bothered to copy that into any submachine guns!

I conclude that SMG designers were just incredibly lazy.

If you actually do the math you'll find that it's extremely difficult to achieve a cookoff in a cased-ammunition, magazine-fed weapon. What I'm not clear on is whether any of the designers during WWII actually knew that.

#15 sf_cwo2

sf_cwo2

    Member

  • Members
  • PipPipPipPipPip
  • 191 posts

Posted 18 July 2011 - 05:10 AM

I'm aware that the G11 wasn't designed with caseless ammo to resists cookoffs.


So, your previous statement was one big typo? I know, I know-- 'which one', right? I quoted it before...

I conclude that SMG designers were just incredibly lazy.


Based on what research? I already listed the reason for conversion of the MKb42 (H) to closed bolt and cited a source. Have you bothered reading any of the design criteria listed for any weapon/design solicited by the Wehrmacht? The truth is out there... go read it and learn for yourself.


If you actually do the math you'll find that it's extremely difficult to achieve a cookoff in a cased-ammunition, magazine-fed weapon. What I'm not clear on is whether any of the designers during WWII actually knew that.


I'm not clear on whether you bother reading my posts as you are regurgitating irrelevant errata from all over the place.

#16 MikeRex

MikeRex

    Member

  • Members
  • PipPipPipPip
  • 82 posts

Posted 19 July 2011 - 04:54 PM

So, your previous statement was one big typo? I know, I know-- 'which one', right? I quoted it before...


To clarify; the propellant (denatured high explosive instead of the usual nitrocellulose) used in the G11 was specifically designed to resist cookoff because the caseless configuration of the rifle was so much more prone to it in the first place.

Which is, by the way, entirely consistent with this statement:

There are other solutions, like the high-ignition propellant developed by Dynamit-Nobel for the caseless G11 rifle



Based on what research? I already listed the reason for conversion of the MKb42 (H) to closed bolt and cited a source. Have you bothered reading any of the design criteria listed for any weapon/design solicited by the Wehrmacht? The truth is out there... go read it and learn for yourself.


I already listed my reasons for thinking this in some detail. Why take the effort to elide them from the quote?


I'm not clear on whether you bother reading my posts as you are regurgitating irrelevant errata from all over the place.


Funny, I was about to say the same.

#17 Poppy

Poppy

    grasshopper

  • Members
  • PipPipPipPipPipPipPip
  • 3,313 posts
  • LocationShambhala http://www.youtube.com/watch?v=hv9DwzU3KP0

Posted 20 July 2011 - 01:58 AM

Found that video:

YouTube - Colt M4/AR-15 Fired Full Auto untill it catches on fire

It's 14 magazines back to back full auto before cookoff occurs. That's 420 rounds at which point the carbine is ON FIRE.

I think the Germans overestimated the facility of magazine-fed weapons to cook off.


That was great. Not sure why. Thanks Mr....Also to sf2. You guys are good reads.

Edited by Poppy, 20 July 2011 - 02:08 AM.





0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users