question 1. Need help with FA MG42 - ejection issues

[bbigbore]

A customer brought me his MG42 and said "it doesnt" work". I've owned a couple MG34s before, but I dont have much experience with the 42 other than reading Volk's books.

This a late war 42, with as far as I can tell all german WWII parts.

I take it to the range, load a belt and after 5 shots it malfunctions with a spent case caught by the bolt in the ejector port. Top cover comes up, belt comes out, pulling on the cocking handle just squeezes it between the case between bolt and lever. I pull the bolt itself back and the stuck falls out. The bolt snaps forward, firing the cartridge that was barrel. (always keep the barrel pointed in a safe direction)

Ok, load another belt, 5 more shots and another stuck case in the ejection port. top cover up, belt out, BARREL removed with live cartridge in the chamber - - then I pull the bolt back dropping the spent case. As I go to put the barrel back, I see the barrel bushing around the middle of the barrel, It broke in half.

I replace the bushing, swap bolts, 4-5 shots and the same malfunction. I swapped around 5 different recoil springs, 2 buffers, 3 different bolts, 3 barrels, and the same thing happens no matter what combo of parts.
The only constant was the ammo, which is '75 romanian.

All the bolts ride smooth, without a recoil spring, when cocket pulling the trigger sends the bolt into the barrel with just the anti bounce spring. I removed the recouperator to check the springs and they were stiff, but not the WWII twisted style, but a beefy standard spring. I asked the owner, and he said he had Naess put his springs in about 10yrs ago, hasn't shot it until just now.

Any help or advice is appreciated. The gun it extracting, the gun is feeding, but the spent case is not being always ejected clear. The only thing I can think of yet is find a different lot of ammo....

[flemgunner]

That ammo should shoot fine, Its all I shoot in mine. Right off the bat Id consider the recuperator. Everything Ive ever heard or seen on em has the standard wound springs. Try the pogo test and see what happens

[K98dkmauser]

this is very interesting ill see what i can find out

[Blanksguy]

bbigbore,

Reading your post, you seem to have an ejection issue/"challange"........with other parts to check.
I read where this gun has been "checked"/partial rebuild......but nothing stated about correct operation at that time....(?).

One of the major issues when operating the MG42 is that the parts are "free" to operate, complete assemblies that are assembled correctly, and have the correct operating hole-sizes/restriction to operate the "system" in the caliber that you are trying to operate in as these will hinder full recoil so that the Bolt's rear will strick the Buffer-Head with enought force to hit the Bolt-s "Spoon" which hits the ejector-rod ....which hit/ejects the empty shell-case..
If the MG42 is not ejecting the cases on a regular basis......I would first start by checking the Booster-Cup/"Nozzle" hole-size (11mm for 7.62x51mm and 14mm for 8x57mm).

It is unknown to me why the Barrel-Bearing broke in the middle......unless it was cracked at some earlier point........its operation should not allow the keys in the receiver-key-ways to strike/crack the bearing in the middle........."unless" the operator tried to fire "Blanks" without a correct 2-pcs Blank-Barrel-assembly allowing the front section to move too far forward (?).

If the MG42's parts are correct .......I would insure that the belts are correct for the caliber and not holding the cases too tightly.
Last, with steel-cased ammo......you will need to insure that the chamber is cleaned often as these cases do not have the lubrisity of Brass-Cased ammo......

Regards, RichardS in MI.
US Army, Retired
Blanksguy2001@chartermi.net

[bbigbore]

The booster cone in the gun, and one that came in (what I was told) was a 8mm Yugo Kit are both have 11mm holes.

As for the booster assembly, I completely forgot to check that while shooting. If it were a notch loose, it could cause these issues....

I assume the "pogo" test has something to do with pressure applied to the barrel bushing with a barrel installed? If you can tell me how to perform the pogo test I'll do that next.

[bbigbore]

The busted bushing was probably just a freak occurrence. The pic shows what I am measuring at 11mm for the booster. Both I have measure the same. I found the pogo test directions and passes with flying colors. The complete gun will rest on the bushing. When I push down and let go it pops right off the concrete and pogos a few times.

[42rocker]

Ok, this might sound stupid but one of the problems that I have read about is bounce back in which a spend case bounces back up and gets caught. Could this be a simple solution? How are you shooting it? Is a bounce back up possible or can this be ruled out? Are you shooting off a bipod or a anti air craft tripod or ??

GOOD LUCK

Later 42rocker

[bbigbore]

Ok, this might sound stupid but one of the problems that I have read about is bounce back in which a spend case bounces back up and gets caught. Could this be a simple solution? How are you shooting it? Is a bounce back up possible or can this be ruled out? Are you shooting off a bipod or a anti air craft tripod or ??

GOOD LUCK

Later 42rocker

I though the same thing, as that happened to me with a MG34 before. I moved from a frozen dirt driveway, to a grass lawn, and from a Lafette.

[JBaum]

All the bolts ride smooth, without a recoil spring, when cocket pulling the trigger sends the bolt into the barrel with just the anti bounce spring.

Are you saying that the bolt goes forward simply by coasting (muzzle down) with gravity? If so, that's good.

Your ammo isn't producing enough power to operate the gun, but that isn't necessarily the fault of the ammunition. Something else is draining the energy away.

There is a barrel stop inside the receiver, ahead of the cam piece. It is a sideways U shaped piece (top of the U is facing the barrel change door) held in place with 3 rivets. It is located under the front sight. Its function is to stop the barrel from going too far forward, which if it does, it beats the barrel bushing to death.

Check it to make sure the barrel isn't being allowed to move too far forward in the receiver. If the stop is beaten forward a bit, the edges battered where it contacts the barrel, or the rivets loose, it could let the barrel move too far forward.

This will drain away recoil energy, and after a few shots (5 in your case), there will no longer be enough spare recoil to push the bolt far enough rearward to properly eject the empty shell. With underpowered ammo, or a gun that's consuming too much energy to operate, the rate of fire will slow as the gun runs out of energy. If the ammo is the cause, quit shooting it because sooner or later bad things will happen (blown cartridge, blown barrel door, blown receiver). Get better ammo. That doesn't seem to be the case. If the gun is at fault, fix it, which is where we're at now.

You may notice (difficult with only a 5 shot burst, but possible), that the first few shots run faster than the last few.

Once again: The 2,000 character limit on message length is CRAP.

Continued in the next message.

[JBaum]

With the barrel in the gun and the flash hider unscrewed, is there a slight gap (40 thousandths of an inch) between the inside of the barrel bushing and the front of the barrel muzzle? There should be. The two should not be tight together (close yes, tight no). If they are, carefully inspect the barrel stop.

Regarding the FA MG42 requiring (requiring is the key word here), a nozzle change depending on caliber, it doesn't. With a 14 mm nozzle, the gun will run slightly slower on .308 than on 8mm, but it will still run just fine because with a properly maintained gun, there's enough extra energy to do that. It will cycle faster on .308 with an 11 mm nozzle, but with an 11 mm nozzle, it recoils a bit harder than necessary when shooting 8mm, so I don't recommend the 11 mm nozzle for 8mm (no sense beating the gun more than it already beats itself).

Most semi 42's are on the edge of having sufficient power to operate, so for them, changing the nozzle makes a much bigger difference, and is often required to keep the gun running with a caliber change.

The recoil booster/muzzle brake is not an adjustable piece of equipment. Screw it on till it's tight, back it off just enough to catch a notch under the lever.

Your pogo test says the recuperator is fine. Bob Naess knows what he's doing, so don't worry about the spring type.

The red flag here is the broken barrel bushing. In your picture of the broken barrel bushing, it looks like the tabs have been beaten (mushroomed out on the forward edge of the tab) in the slots from the bushing being hammered forward in the slots of the receiver bushing. Is that correct?

[flemgunner]

HHmm didnt know that about the nozzle with the 308. Ive actually never tried 308 in a gun that was "set up" for 8mm. Now Im gonna have to try it

[bbigbore]

regarding the bolt movement, I'm saying with no springs, or sear/trigger group, the bolt moves/rides freely on the rails. There are no tight spots or binding. The trigger/sear/safety all work properly.

The bushing has no worn/mushroomed edges, I figured it was just poor quality material.

The barrel stop looks good as new. There is a slight rub mark that is only visible with the camera at 8X zoom.

With the barrel out of the gun, the bushing drops into the receiver, stopping on the bottom of the lever for the muzzle cap. With the barrel installed, the bushing is pushed out by the barrel. If there is nothing to support the bushing other than the barrel, how can there be a gap? With all installed, it wiggles around, but I dont see a gap?

I just went and checked it again....

With the gun horizontal, and the barrel installed, I can pull the bushing 40 thousandths beyond the muzzle back and forth freely.

The more I think about it, I NEVER checked the booster/muzzle and to see if it was as tight as it could be in a final notched position. I'm hoping a loose booster in combo with the outside temps being in the teens was my main problem. I'll wait for it to warm up and try again.

Thanks for all the help so far guys.

[bbigbore]

bushing/muzzle gap

[JBaum]

Good pictures - it looks like a correct fit.

Have you checked the ramps on the cam piece. They push the rollers inward when the barrel recoils. Sometimes they can have a chip so that the bolt isn't unlocking from the barrel correctly.

[42rocker]

Don't have a full auto and still learning a few things from this thread. Thanks for the info.

Later 42rocker

[bbigbore]

the unlocking surfaces are smooth as glass. I can really only get a good picture of the left side, but can see the right looks the same.

[bbigbore]

I braved the cold one more time, and still NO LUCK! I swapped, barrels, bolts, boosters, flash hiders, buffers, and I'm having the exact same problem no matter what the combo. I ran it with the booster as tight as it would go, I backed the flash hider off 3 notches(I think it seemed to run faster with the loose flash hider?), I get the same thing every time. I took 2 different lots of Romanian, and Brass Yugo 8mm, new and WWII belts.
The only piece I havent swapped is the recuperater/springs. Could the springs in there be too tight?

http://72.240.4.142/random/nogo.wmv clips of the gun firing. EVERY stoppage is exactly as shown in the attached pics.

[JBaum]

Take off the ejection port door and try it again. Really. It comes off easily. Take off the trigger grip and slide the pin out while you pull the spring arm from the notch. The door comes off while still on the pin.

It's possible the door is bouncing around enough to get in the way of the ejecting shell. That's one of the things that can happen that's listed in the MG42 armorer's manual.

[bbigbore]

Good idea. The spring on the door is broken, it flops all over the place right now.

[JBaum]

Right there is your problem. The door bounces around and partially closes the ejection port, causing a shell to not be able to eject. I did a very slow view of the video of you shooting in the driveway with the house behind you (1/8 speed). The gun stops shooting and the ejection port door is closed.

The door isn't necessary. Take it off, or get a good spring for it. I'd bet the gun will work now.