The Firing Line Forums

Go Back   The Firing Line Forums > The Hide > NFA Guns and Gear

Reply
 
Thread Tools Search this Thread
Old November 5, 2017, 06:30 AM   #1
simonrichter
Senior Member
 
Join Date: December 3, 2011
Location: Austria
Posts: 757
Recoil operation in machine guns

Just wondering why most armed forces worldwide now utilize gas-operated infantry-role MGs - I only know of the Germans and Austrians still using a blowback-operated 7,62 version of the WWII MG42, yet there are no true new developments.

I it simply the weight or are there other issues with recoil operated MGs as compared to gas-operated?
__________________
"Get off of my lawn!" Walt Kowalski
. ISSC PAR .223
simonrichter is offline  
Old November 5, 2017, 01:54 PM   #2
mete
Senior Member
 
Join Date: June 14, 2004
Location: NY State
Posts: 6,575
Much of what you refer to as ' blowback' is actually 'delayed blowback' . The MG42 and a number of guns developed by H&K are delayed blowback from machine guns to pistols like the great HKP7 ! Rifle cartridges like the 7.62 would require a good bit of weight to deal with the higher pressures .
__________________
And Watson , bring your revolver !
mete is offline  
Old November 5, 2017, 08:23 PM   #3
ttarp
Senior Member
 
Join Date: January 4, 2013
Posts: 888
The MG42 is a roller locked recoil operated MG, the Hk designs are similar, but the barrel doesn't move rearward to unlock the rollers, hence delayed roller blowback as opposed to roller locked.

The MG3 is used more in a reserve status rather than front line is it not? Gas operated MGs should be softer shooting and thereby more accurate than a recoil operated MG. Another thing to consider is which design is easier to maintain(I don't know, just throwing it out there).
ttarp is offline  
Old November 6, 2017, 12:50 PM   #4
simonrichter
Senior Member
 
Join Date: December 3, 2011
Location: Austria
Posts: 757
The right term is "recoil operated", not blowback, indeed.

While the MG3 is being replaced by the gas-operated new MG5(made by HK) in the German Army, in Austria the MG74 remains the one and only multi-purpose MG.

Not sure but I'd guess the recoil-operated system is easier to maintain and clean, compared to gas-operated systems with their pistons and gas ports...
__________________
"Get off of my lawn!" Walt Kowalski
. ISSC PAR .223
simonrichter is offline  
Old November 7, 2017, 06:31 PM   #5
44 AMP
Staff
 
Join Date: March 11, 2006
Location: Upper US
Posts: 28,677
Quote:
Gas operated MGs should be softer shooting and thereby more accurate than a recoil operated MG.
Might be, but it doesn't matter.

When you are talking belt fed, the lightest guns are in the 20lb class, and older designs are 30lbs or even more. The weight alone makes them "soft shooting", and the fact that they are normally fired from a bipod or tripod.

More accurate?? Accurate machine guns, in the rifle sense of accurate, are the last thing the military wants, or needs. They don't want a machine gun that will put all its bullets in one hole, or even close. They want a "cone of fire", a "beaten zone" with the bullets dispersed to cover a given area.

The classic example of this is the Browning M2 .50 caliber machine gun. For a machine gun, its "rifle" accurate. In order to meet military needs, the ammo is made with a large tolerance for bullet weight. This dispersal factor meets military needs better, and does not require changes/modifications to the gun.

Both the gas and recoil systems have been around a long time. The first machineguns were recoil operated (Maxim) but gas operated designs showed up soon after.

Both systems can be done well, or done poorly. Since the end of WWII, gas operated guns have come to dominate the .30 caliber class, because they can be lighter than the older recoil operated designs, but that is mostly due to other features of the guns, not the gas system alone.

The old Browning recoil operated guns are built like tanks, and weigh nearly as much, but they run almost forever. The M60 is much lighter, gas operated, and a piece of crap, compared to other designs.

The M2 Browning .50 is still in front line service, despite over 90 years, no one has built anything significantly better.

The #1 reason a Browning M2 stops working is, it runs out of ammo
The #2 reason a Browning M2 stops working is, it runs out of ammo.
The #3 reason a Browning M2 stops working is, the thing it is mounted on gets blown up.

A bit of a joke, but not without a grain of truth.

I worked on them for a few years in the Army, as a Small Arms Repairman. Always had M2s in the shop, needing to be fixed. Never ONCE had one in the shop where the firing or feeding mechanisms were broken, not once. EVERY M2 we got was broken by troops dropping them, bending/breaking sight ears, charging handles, or, once, the rear spade grip frame.

Lighter weight, smaller caliber belt feds rule the infantry assault niche, best for CQB, but for range, and power, its tough to argue with a heavy .50 cal, and "Ma Duece" is the best there ever was.
__________________
All else being equal (and it almost never is) bigger bullets tend to work better.
44 AMP is online now  
Old November 7, 2017, 09:34 PM   #6
James K
Member In Memoriam
 
Join Date: March 17, 1999
Posts: 24,383
Machine guns are intended for area fire, not accurate single bullet placement. The original BAR, with its bipod mounted back on the handguard, was so accurate that it could literally put a whole magazine into an enemy's coat button, a waste of 19 rounds. The reason the bipod was moved to the muzzle was specifically to spoil the accuracy and, as one writer put it, "spread the blessings around."

Jim
James K is offline  
Old November 7, 2017, 09:57 PM   #7
ttarp
Senior Member
 
Join Date: January 4, 2013
Posts: 888
Ok ok, point taken, the horse has officially died, no need to take it further

Not doubting you, but that seems a little counter intuitive about the bipod placement. Keep in mind, when I say something ignorant, the only experience I've ever had with a full auto firearm was a 50 round belt on an MG42 at a shoot last year, I'm here to learn.
ttarp is offline  
Old November 8, 2017, 01:23 AM   #8
44 AMP
Staff
 
Join Date: March 11, 2006
Location: Upper US
Posts: 28,677
Quote:
Not doubting you, but that seems a little counter intuitive about the bipod placement.
Why would you think that? And, I'm not trying to pick on you, just trying to understand where you're coming from. I was a machine gun repairman for Uncle Sam for a few years in the 70s, and they have always interested me, so I've got a little more experience with their designs and operation than many people, including some infantry machinegunners, who, no doubt know their service weapon well, but often don't know a lot about other guns or design principles.

First, take a look at sporting rifles, particularly varmint rifles, which are often used with a bipod. Where is the bipod mounted? NOT on the barrel, but on the stock, usually on the QD sling swivel stud. The function of those rifles is to be accurate. Mounting the bipod on the barrel works against that.

Has it been done, is it done today, yes, on military arms, where pinpoint accuracy isn't the requirement. (and also as a cheap plastic clip on for .22s) But not when accuracy is important. Even mounting a bipod on the stock can change the point of impact to a degree, but stock mounting seems to be more consistent and affects shot to shot accuracy less than barrel mounting.

With a machine gun, where the object is not to put 20 shots in a group you can cover with a quarter, but to put those 20 shots scattered over a couple square feet (and in one to two seconds) the effect of a barrel mounted bipod on accuracy is usually insignificant, because the overall design of the gun isn't all that accurate to begin with.

Browning machine guns were kind of an exception, even in their heyday, they were exceptionally well made and accurate. Remember that in the pre-WWII world, military arms were made like civilian arms. Heavy steel, made to last, and generally accurate to very accurate.

War time experience taught every nation's military some important lessons, one of which was, building quality machineguns like traditional sporting arms was a waste of money. Guns (all of them) get lost in combat /damaged /destroyed at a huge rate, they almost never survive long enough to actually wear out from use, WWII taught designers the value of guns made cheaply, which would last "long enough" and if cheap, could be easily replaced. (and note, I'm speaking primarily about infantry machine guns here.)

WWII proved the value of guns made with light metal stampings as major components. Not only were the guns lighter weight (and therefor better liked by the guys who had to carry them), but they could be made faster, and cheaper than the more traditional guns. When bullets fly, armies learned that "works good enough, and is cheap" was better than "costs more, but lasts". That lesson is still with us today, at least, when it comes to small arms.

There are several "classes" of machine guns, and some armies class the same gun different ways, depending on its intended use. Some guns cross classes, and some are kind of in a class by themselves.

The general classes are Light and Heavy, based primarily on the overall weight of the gun system, but also taking certain other features into account. Light machineguns include many belt fed and box magazine fed designs. They are intended for intermittent full auto fire. Heavy MGs are belt fed, intended for more sustained fire (many were water cooled). Caliber also plays a role in classification, as .50 /12.7mm /13mm are considered heavy machine guns, even when air cooled and built as lightly as practical.

The Germans introduced another class, just before WWII, the GPMG (general purpose MG), where the same gun (MG 34, and later MG 42) were considered a light MG when fired off the bipod, and a heavy MG when used with their tripod mount (and optical sight).

I love to talk machine guns, and will go on at length, if you don't stop me.

What do you want to know??
__________________
All else being equal (and it almost never is) bigger bullets tend to work better.
44 AMP is online now  
Old November 8, 2017, 12:08 PM   #9
ttarp
Senior Member
 
Join Date: January 4, 2013
Posts: 888
I don't want to rabbit trail Simons thread, but so you know where I'm coming from, I'm just a casual shooter that collects firearms I find unique or interesting.

And yes, I realize wikipedia isn't the best source for accurate information, but this is posted from their page on the FG42(apples to oranges comparing a paratrooper rifle meant to be a jack of all trades to a purpose built MG).
Quote:
After approximately 2,000 FG 42s had been produced by Krieghoff, supplies of the manganese steel from which the receivers were forged were diverted to other needs; this meant a redesign was required to use stamped sheet metal in its place. Field reports were also requesting minor improvements, such as: relocating the bipod from the front of the handguard to the muzzle to reduce shot dispersion;
Obviously there is a huge difference given the FG42 weighed less than half as much as the MG42, but I thought the same mechanics or physics applied, hence my comment. I understand keeping weight or pressure off of the barrel for accuracy, but being influenced by the above, my assumption was the further out a bipod, the more steady it would be. Anyhow, thats where I'm coming from.

Whats your opinion on the development and (seemingly) preference of gas operated MGs over recoil operated designs like the MG3 or MG74?
ttarp is offline  
Old November 8, 2017, 03:11 PM   #10
44 AMP
Staff
 
Join Date: March 11, 2006
Location: Upper US
Posts: 28,677
Quote:
relocating the bipod from the front of the handguard to the muzzle to reduce shot dispersion
OK, I get it now, I think. What you're missing is the difference between a barrel mounted bipod's affect on the mechanical accuracy of the gun, and its ability to enhance the user's accuracy with the gun.

In the case of the FG 42, its being used as a light weight, full house (7,92x57mm) full auto, and rapid fire semi auto, where the forward mounted bipod's aid to shooter accuracy overcomes the much smaller effect on the barrel's accuracy. These aren't MOA precision rifles, and that's where the bipod's effect on accuracy is most pronounced.

An interesting thing to me is that this thread is the first time I have heard that the reason for moving the BAR bipod to near the muzzle was to reduce the accuracy. Then again, the BAR is a very unique weapon in many ways.

I believe you are correct, that the muzzle mounted bipod increases the overall stability of the weapon when fired, and that increases the shooter's ability to get hits on targets.

And it is something you can do much more easily with a gas operated gun. To do it with a recoil operated gun, you need a barrel jacket to mount the bipod on, which adds to the size and weight of the weapon.

My opinion on gas operated guns (and the preference for them) depends on which guns you are talking about. Some designs are very good, some not so much.

One of the reasons there is such a preference for them today is the bipod thing, since a bipod is a very desirable feature in a LMG. There are a couple different approaches used. Actually attaching the bipod to the barrel, or mounting it on the front end of the gun, such as on the front end of the gas system.

A good design allows you to swap out heated barrels quickly and easily. The importance of this is better recognized today than it was in the past (pre WWII designs).

HOWEVER, despite having the right ideas, it can still be done wrong. Again, I must point to the M60 in this regard.

Changing the barrel on the M60 is simple, one latch, pull it out, put in another. BUT, they put the handle on the receiver (where it works just fine as a carry handle) not on the barrel, where it could be used to remove a hot barrel, as well as be a carry handle. SO, there had to be an asbestos mitten issued with every barrel, to handle it when it was hot. An extra item desperately needed, but easily lost in combat.

Also the M60's barrel mounted bipod and gas cylinder meant each spare barrel had to be bigger and heavier, and cost more, than a design where the barrel alone is swapped out.

On the other hand, the higher cost for each barrel assembly meant more $$$ for the supplier. In some people's eyes, that's a win...
__________________
All else being equal (and it almost never is) bigger bullets tend to work better.
44 AMP is online now  
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 06:05 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
This site and contents, including all posts, Copyright © 1998-2021 S.W.A.T. Magazine
Copyright Complaints: Please direct DMCA Takedown Notices to the registered agent: thefiringline.com
Page generated in 0.08578 seconds with 10 queries