U.S. Marine Corps Fielding Improved M2 .50 Cal. MG

Kitup.military.com ^ | 28 Apr, 2017 | MATTHEW COX

[archy]

That was the nice thing about the M-85 version of the .50 cal on the old M-60A2, it had a set head space and timing, no need for a guage or the M2 adjustments.

The switchable slow-rate/high rate flip lever on the back of the receiver was a nice touch too, supposedly for antiaircraft fire. On the tanks we used it like a long-range 1000-meter shotgun in five-second, 100-round bursts, then changed barrel and belt.

[archy]

What ever happened to water cooled machine guns.

The last general use of watercooled MGs in US service was with the .30 caliber M1917 Browning watercooled, more accurate than the air-cooled guns due to the front barrel bearing surface at the front end necessitated by the need to keep the front gland packing watertight, but just loose enough to let the barrel cycle in recoil. The guns were used for overhead fire at basic training centers as trainees beneath crawled on the ground through the barbed wire as tracers flipped by overhead to the accompaniment of 1/4-pound demolition charges being set off in sandbagged pits. Both the added accuracy and ability to run 30 and 50-round bursts were features not possible with the air-cooled M1919A4 or M60, at that time, 1966 or '67. We used to refer to the MG firing detail- at night- as machineguns a-go go, with the fiddlers three, 3 guns being used to cover belt changes or possible stoppages, just like in the real world.

[archy]

Possibly - the MG1 version in 7.62mm NATO, more likely.

The issue would have been whether that crazy high rate of fire would have really been effective in an expeditionary environment.

What, the American T24 developed by Saginaw Steering Division of GM wasn't good enough for you, and you like the reworked WWII guns better? They got the cyclic rate of an MG42/MG1/MG3 down to 900 RPM with a heavy bolt and modified buffer, helpful for groundpounders who have to carry their own ammo and spare barrels, but as a tank coaxial gun, the ability to let off a 30-round burst in under a second and a half was thought to be a good thing. The belt tray on the inside wall of the turret where the co-ax belt was fed from carried 6000 rounds[ we carried about two refills in ammo cans on the turret basket floor, sometimes more.

[archy]

Primary headspacing is usually set as you describe - where the barrel and receiver join (at least for most 20th-century military rifles). There are oddballs, though - in tilting-bolt designs like the SKS and the FN-FAL, headspace is tweaked by adjusting the thickness of the bolt locking shoulder. The HK G3 (HK-91) and its small-bore relatives rely more on bolt-to-bolt carrier gap than headspace, due to the roller-locking design being adjustable with different diameter rollers.

And as on the British Number 4 series Lee-Enfield rifles, that use interchangable front bolt faces in different graduated lengths to make the adjustment, used with the rimmed .303 British MkVII cartridge. Works like a charm, all you need is a headspace gauge and a selection of bolt heads.

[Charles Martel]

I recall first reading your comments on the No. 4 Lee-Enfield over on the Tom Bowers “Sword of Damocles” message board. Interest in the No. 4 as a SHTF rifle had bubbled up there for a while. Might’ve been during the run-up to Y2K.

[NorthMountain]

Parrott Rifle:

[archy]

Parrott Rifle:

Avoid.

Metallergy and flaw testing had not really reached the state-of-the-art for artillery barrelmakers then.

[NorthMountain]

If that can be called a “rifle” (and it was), you should have no qualms about labeling your 105 a “rifle”.

[archy]

“The improved M2A1 makes Marines more lethal because they’re able to get rounds down range quicker. Marines will have better mobility because of the fixed headspace and timing—it’s much quicker to move the gun from position to position and put it back into action. Because they’re less exposed, Marines will have better survivability too.”

Now if we can just get them to quit using live .50 rounds as drift punches when knocking the gun retaining pins in and out when removing/installing the gun on/from a vehicle mount.

[archy]

I recall first reading your comments on the No. 4 Lee-Enfield over on the Tom Bowers “Sword of Damocles” message board. Interest in the No. 4 as a SHTF rifle had bubbled up there for a while. Might’ve been during the run-up to Y2K.

My *Gunsmoke* columns ran pre-Y2K, which was the point. One covered the SMLE/#1 Mark III pretty well, comparing the SMLE my kid got for his birthday with another one, though I never got into the #4 in great detail. I had around 4 then, including a US-built Lend-lease Savage #4 MkI* and a like-new Canadian Long Branch, and shot them often, mostly running the then-availabe Greek surplus HXP and my handloads on the same brass. I've got an eye out for a #5 Jungle Carbine for Wyoming bear insurance, but if I don't run across one, a #4 or Garand will certainly handle that job.

[archy]

If that can be called a “rifle” (and it was), you should have no qualms about labeling your 105 a “rifle”.

Oh the Parrott's were rifles, for sure, and their accuracy was an evolutionary improvement of the smoothbore Napolean field pieces that were par back in that day. Even the main battery of the USS Iowa-class battleships' 16-inch guns were rifles, as were our divisional artillery 155mm,8-inch and 175nn howitzers and SP guns. It's just that the larger Parrot guns had a reputation back then for catastrophic failure.The advances in large bore rifling and other machine techniques did not extend to increased strength.

In 1966 I was tasked with being part of an Armor firepower display intended to impress the petunias out of visiting West Point cadets, prospective Armor officers on graduation.Since they had their issued binoculars I got to show off first, demonstrating the capabilities of the weapons of the M48 tank, concluding with nailing a Coke bottle atop a six-foot-high sawed-off phone pole with a solid practice dummy main gun round from 800 meters, easy with a 10x scope and a 50-ton bipod....

Then the 4 other tanks of a platoon pulled in alongside, 2 from the left, 2 from the right, and opened up, and we shot every scrapped-out target truck and impounded car that had dragged he range for the last two months; don't get your car towed by the MPs at Knox. And for the final display of treadhead attitude after the last rounds had been fired there was a little group of five or so standard humanoid target in a cluster apparently overlooked. Not so.

We all started up, two tanks returned left and two turned right- and we were up to about 30 mph when we got to the targets and spun a hard-locked neutral turn spin squashing the targets like cardboard, which, of course, they were. Some of the cadets in the observation bleachers stood up and cheered; those were the ones we wanted for tank platoon officers.

[Chainmail]

Thanks for the picture and data on the T24: neat development - but I can guess why it wasn't accepted for our service.

Its recoil operation. Gas operated guns allow different cyclic rates - the M240G/FN-MAG allows three different rates of fire with a simple adjustment but with the MG42/1/3 you just have one choice - fast. The high rate is only useful for short periods and straight at the target. Because of space/weight limitations with the infantry, ammunition is limited and high rates reduce the length of time your machine gun will be effective. In defensive positions where interlocking, grazing fire is used to provide final protective fires, high rates of fire only provide a short period of use.

I like the barrel change system for the MG42 - straight to the rear, so you don't have to get above the level of the gun to change barrels. Other than that, advantage M240G.

[Chainmail]

Great story! Only one tiny niggle: the M107 175mm SP gun was absolutely NOT a howitzer..

Howitzers are artillery that is easily capable of firing high-angle and low-angle fires, sort of like a cross between a gun and a mortar. The M101A1 105mm was a howitzer and maybe the M114 155mm too - and I know that the M198 and the M777 are called howitzers but in real life are almost never fired above 900 mils.

Really pushes the definition of a "howitzer" to include weapons that can't be elevated easily and then can't be loaded at high elevations and the projectile loses stability at max ord..

[archy]

Thanks for the picture and data on the T24: neat development -

You're welcome!

but I can guess why it wasn't accepted for our service. Its recoil operation.

Nope. Funny story. I'll get to it.

Gas operated guns allow different cyclic rates

So do recoil operated guns, but it's arranged differently. One of Maxim's early water-cooled guns included a clockwork buffer retarder on the lockwork, and it was infinitely adjustable via a sliding bar from about a shot every second to 10/second- about 600 RPM. Later the Germans set the rates of fire to match as closely as possible the max RPMs of the motors in their WWI aircraft, then fitted a mechanical interrupter gear to allow the gun to fire through the arc of the propeller without hitting it. Later, a second gun was set up the same way, and the fighter pilot had progressed a step between gentleman officer pilots taking potshots at each other with their pistols.

Browning's M1917A1 was lightened into a lighter air-cooled gun as a burden a little lighter for the Cavalry's horses to haul [and got more ammo added to their load, ya can't win!] and by 1940 was modified into a 1200 RPM gun for the rear gunner in torpedo and dive bomber aircraft. A few- five at least- were also fitted with cutoff M1 Garand buttstocks and bippods and used as Infantry guns, with which one Marine earned the medal of Honor. The Austrian and German MG42 followons use differing bolt retarders and weighted carriers to go from around 1500-1750 RPM to 800-900 RPM, tankers and antiaircraft gunners wanting the faster rate, Infantrymen who carry their own belts preferring the guns *set slow;* the Austrian guns have a single-round selector built into the trigger group of their MGs

But we encountered the MG42 in North Africa in '42, and it was considered as a lighter MG for American Infantry on its bipod and as a light .30 Browning replacement on some vehicles. So Ordnance contracted Bridge to run off drawings and a set of test stamping dies and with the help of a couple of captured German guns, the drawings, dies and two prototype guns were made. They didn't work very well.

The US cartridge of the time was the .30-06, .30M2 version by the time WWII came around, aka 7,62x63mm to the EuropeansThe German guns, and their receivers so carefully copied, were understandably designed around their 7,92x57mm Mauser caertridge. The difference between the empty cases is 6mm, about a 1/4 inch, just enough for the longer US empty casews to catch on the edge of the edge of the ejection port- and due to the location of the barrel catch, it couldn't just be opened up, though the use of a shorter barrel carrier had been discussed. But the good idea was dropped, and the guns transferred to the museum at Aberdeen Proving Ground.

Come the 1950s, we'd won the war, and had a new possible enemy to fight. We decided it was time to have a lighter rifle than the M1 Garand, and full-auto as well, and we got a new cartridge to go with it, one that was about 3/8 of an inch shorter than the old .30-06 used in the Garand. it would have worked in the T24 guns. Instead we spent half a billion dollars designing and manufacturing the M60 MG, heavier, less reliable and about three times as expensive as an MG42, and not suitable as a tank or light armoured vehicle mg because the barrel slides forward for replacement when hot. Eventually, they were replaced with FN MAG guns that became the M240, also heavy, but it works.

But we could have had the T24 in 7.62x51 NATO as early as 1955. And saved a good part of that 500 million dollars.

Those German bringback guns that gave up their parts to get the prototype T24s going? They went to the Aberdeen Proving Ground museum too, along with their leftover parts. When Colonel Jarrett, the museum director retired, he took a pretty fair-sized truckload of souvenirs with him as a retirement present. A close friend of his got one, and he passed away a few years back. And I know where it is. But I see nossing, NOSSING!!!

[archy]

Great story! Only one tiny niggle: the M107 175mm SP gun was absolutely NOT a howitzer..

Exactly so. Which was why I wrote:

...battleships' 16-inch guns were rifles, as were our divisional artillery 155mm,8-inch and 175nn howitzers and SP guns.

Honest! I can make enough mistakes without being called out over a conjunction not precisely linking the 175s [we called them the division sniper rifles] to SP guns. Proof being the comma I left out between *artillery* and *155,* as well as my ham-handed typo of turning the 175 into a 175nn tube.

I concur that that gun-howitzer divide is narrowing. So is the one between howitzers and mortars. And terminally-guided projectiles are making accuracy considerations of possible less importance as well.

[archy]

Great story! Only one tiny niggle: the M107 175mm SP gun was absolutely NOT a howitzer..

Exactly so. Which was why I wrote:

...battleships' 16-inch guns were rifles, as were our divisional artillery 155mm,8-inch and 175nn howitzers and SP guns.

Honest! I can make enough mistakes without being called out over a conjunction not precisely linking the 175s [we called them the division sniper rifles] to SP guns. Proof being the comma I left out between *artillery* and *155,* as well as my ham-handed typo of turning the 175 into a 175nn tube.

I concur that that gun-howitzer divide is narrowing. So is the one between howitzers and mortars. And terminally-guided projectiles are making accuracy considerations of possible less importance as well.

[Chainmail]

I have worked with APG in the recent past but more with artillery projects than small arms. I actually worked on a project to convert the Soviet D-30 howitzer into a 127mm weapon firing the Navy's 5"/38 ammunition as an alternative to the "Lightweight" 155mm project!

I think that the MG42/1/3 is a good, solid weapon but doesn't fit the methods of employment within our (US Army and Marine Corps) doctrine. It would have been less expensive to produce than the M240 but at the end of the vendor pipeline, who knows? No need to replace the M240, though - it's an excellent machine gun and it's proving to be the best that we've ever had.

The M-60 was a cheap and flawed weapon but we made do with it. I used the M-60 in combat a lot and got quite good with it. I suppose I could have made do with the Benet-Mercier too, but that's because we are just used to pounding square pegs into round holes.

Semper Fi.

[servantoftheservant]

awesome post. Love the background and detail you provide.

[archy]

No need to replace the M240, though - it's an excellent machine gun and it's proving to be the best that we've ever had.

They're pricey, which goes with the territory when you pick a Porsche over a Yugo or Kia. I've carried and used British Gimpys, Israeli and Rhodesian MAG58 *MAGgots*, and American M240G and M240E4, worked on the JSSAP Program on what became the M240C coax gun program for Army M60A1 and Abrams tanks, and I've shot the M240L, which I don't care much for.

I've shot both Springfield and Colt Benet-Mercie M1909 machine rifles too, a personal joy since my maternal grandfather was one of the participants at the 1916 raid by Pancho Villa forces at Columbus, New Mexico, while grandda was trying to peddle electrical lighting and generators [*dynamos*] to the railroad there. His diary reflects his dissatisfaction with the double-barrelled shotgun he used that night, and his intention to pick up a pump Burgess or Winchester. He did, and I still have it; grandson'll get it soon.

The 30-round stamped sheet metal feed strip of the Hotchkiss/Benet guns was problematic, but not such a bad deal when you consider the metallurgy of V-fold magazines of the time such as the ten-years-later BAR and Chauchat. American .30-06 ammunition was at least consistent, unlike the French Hotchkiss guns 8mm Lebel ammo, which has also helped ruin the reputation of the CSRG *Chauchat* which I've actually had pretty good luck with, also when fired with decent ammunition.

It'd help if the M240 was about 10 pounds lighter, like the Russian PK/Pecheneg, and fed from both left [Abrams M240C co-ax] or right [Bradley co-ax] side for vehicle guns [not sure about Marine LAVs and Amphib landers] as per the M2 HB with a simple little bolt switch for feeding, or the 1950's-'60s .30 Browning M37 co-ax guns. The recent Navy attempts to turn the M249 SAW into a 7.62 beltfed may be a step in that direction, but notice that the Marines decided that even the M249 was too heavy- with ammo- for the Marine fire team.

We had this conversation about *ideal* GPMGs over at the WeaponsMan blog a month or two black, with good points made by all. Blogkeeper *Hognose* there passed away over the Easter weekend. It was like having a great technical library burn to the ground with all the knowledge within it lost.

[Chainmail]

You have a fascinating depth of experience and knowledge of firearms - I am probably your closest competitor but I am still learning.

My grandfather, mother's dad, served in WWI on the Texas border as a radio intercept tech, catching the German messages to the Mexicans. Later, he was shipped to Murmansk to aid the US contingent against the Reds with his radio intercept expertise.

My experience with the CSRG was when I was helping the new curator of the War Memorial Museum of Virginia accession and clean his massive weapons collection. The had an "American" Chauchat in .30-06 with its straight magazine and it was locked up solid. I carefully built a big spring compressor and eased that little buttstock off and slowly released the spring pressure and figured out how to disassemble the bolt and carrier. I fumbled my way until I realized that the bolt was assembled improperly and I cleaned and oiled everything and reassembled - and then noticed a folded piece of paper inside that tiny buttstock. The note said "My name is Lt. W.D. Wittmer and I carried this gun in France. I assembled it wrong so you'd find this note". Never did find out what happened to W.D. Wittmer but his weapon and note were on display together after that.

Lighter is not necessarily better for machineguns. The mass reduces felt recoil, makes it steadier for better accuracy and control and the heavier barrel makes it a better heat sink so you can shoot it longer before you have to change barrels.

It's better to make my Marines stronger to carry the heavier gun than it is to have a very light gun that fails.