Maylaisian 7.62 NATO case seperation in MG42

[Waffentag]

Thanks Frank for the detailed reply.

The first thing that I did after I got the gun was to have Bob rebuild my recuperator with his new springs.

At first, the Malaysian was tearing off in the middle. Last time out, Some of the Malaysian and 2011 Lake City tore off near the base the rest tore off in the middle.

So, if I do have imperfections in the chamber, what can I do. 3 of the barrels are marked with a "C" and appear to be chrome lined.,

Thanks Pat

[amafrank]

Most of the 308 barrels I've seen came from Austria and were for the MG74. They are license built versions of the MG3 with a few mods like the finned barrel bearing sleeve and the fancy trigger housing with single shot capability.
In any case the barrels may or may not be chrome lined and won't likely have any issues with rough chambers. They were all built during peacetime....or relative peace time as in cold war. Quality is excellent too.

I guess the only thing you can really do is make a chamber cast with cerrosafe and see whether there are any problems with the chamber. You can measure the diameters at various points to insure the taper is correct and there aren't any swelled areas.

If the chambers are fine and your headspace is within spec than likely the ammo is your problem. I've heard of some problems in the Lake City 50 cal brass but I haven't shot much 308 for a while so I don't pay any attention. Check some of the ammo boards and reloading sites to see if anyone knows of issues with the 308 brass. It is possible.

Find ammo the gun likes and shoot it. Some guns are picky and others not so much. I've got a couple rifles that will shoot about anything out there and a couple others that are one brand guns. It happens.

Last thing.....when you have cases separate are you getting gas blowback into the receiver? If you are is it popping the topcover or blowing crap out the ejection port? If not than my guess is you have a brass issue more than anything else. Some doesn't stretch well.

Hope that helps

Frank

[SturmHead]

Myself and another member here got together yesterday to test the Maylaisian ammo and some other ammo. We both ran the Maylaisian ammo through our MG42s with no issues. I used 4 different barrels including the one that I had had issues with. We both concluded that the ammo was OK to use, but keep a ruptured case extractor handy. All the barrels I used had the head space checked with the bolt used, and were OK.

[Waffentag]

Thanks for the report on the Malaysian. If you don't have ammo problems, it could be a bad Lot or two of my barrels?

I have five 7.62 Barrels, two seem to be the problem. I inspected them, Gave them a good cleaning, tested headspace again. I even installed and tried a MG3 BW HK Marked Cam Piece, ("RTG Description "MG3 TRUNNION COMPLETE")

I just got a few new parts from RTG, and cleaned them again, Will give those two barrels another try, I noticed that the MG3 Bushing was a bit different?

I doubt any of these parts will make a difference?
1 MG3 BARREL BUSHING (MGG-0901)
1 MG RECOIL SPRING NEW (MGG-1824) NEW in the WRAP
1 MG3 MG42 BUFFER NEW IN WRAP (MGG-1774)

[SturmHead]

As long as the barrels and bolts head space are in specification then I think any issue with Maylaisian ammo is the ammo.
Years ago I bought a case of Maylasian ammo for cheap, at the KCR MG shoot. I was talking to a fellow MG 42 shooter, and without any mention of Maylaisian ammo, he told me not to shoot it in the MG42, that it would blow the gun up. Another friend of mine that I trust he knows his stuff, said if it's not NATO ammo (circle and cross on the head stamp) then you can't guarantee it is NATO spec. I thought about what these two gentlemen said and thought "cheap ammo with a bad reputation in an expensive gun, do I want to risk it". I gave that case of ammo away.
Now I know there are some non NATO countries that make fine ammo that will run very good through the MG42; Brazilian military 7.62x51 comes to mind, but Maylaisian is not at the top of my list.
I feel pretty good about the lot of Maylaisiasn that I have, which is almost gone, and wont blow the 42 up, but case separations are a possibility.
I MIGHT buy some more, but 10 to 20 cents a round more buys a lot of peace of mind.

[Waffentag]

Roger that, I had LC separate as well. The Malaysian, seemed to separate in the middle and the Lake City toward the base?

So, I suspect that even thought the bolt barrel combinations head space good, two of the barrels have something going on. I followed Franks instructions and gave the chambers a super cleaning to get rid of any brass build up.

I will test with LC first, then if that works in those two barrels, then try the Malaysian<

The last thing to change is the Recuperator, It is the Original German WW2 that had new springs put in by Bob Naess, I could always have him re-spring a spare from a Yugo kit and try that?

[Waffentag]

This weekend, I am going to try the MG42 again to try to solve the case separation problem.

Last time, Of my 5 barrels 7.62 Barrels, 3 barrels had no case separation, 2 barrels had case separation with both Lake City and Malaysian. I want to verify the three barrels that tested good and see if any of my changes help with the other 2 barrels.

I inspected those 2 barrels, gave them a good cleaning, tested headspace again. They look clean and smooth.

Also, I swapped out the following parts, will any of these changes make a difference?
- MG3 HK Marked Cam Piece, ("RTG Description "MG3 TRUNNION COMPLETE")
- MG3 BARREL BUSHING (MGG-0901) (Has a groove, looks different longer?)
- MG3 RECOIL SPRING NEW (MGG-1824) NEW in the WRAP
- MG3 BW BUFFER NEW IN WRAP (MGG-1774), also got the stock

The Recuperator Spring was rebuilt by Bob Naess a few years ago.

I am currently using the current production MG3 Bolt Catch/Stabilizer with the short current production ejector bar.

Question on Bolt Catch/Stabilizer: If I used the early type bolt catch with the longer ejection bar, would that allow a little more time for the case to shrink away from the chamber walls and help prevent the case from sticking and separating?

[amafrank]

None of those pieces are likely to change the operation as far as case head separations are concerned. They don't really affect any of the pertinent operations.
The mainspring may help if you have feed issues but won't change they way the bolt unlocks.
The trunnion shouldn't change anything unless the one on your gun is really bad. Wear tends to retard unlocking too so if anything a new trunnion (unlocking cam) will cause the bolt to unlock sooner.
The barrel bushing has very little to do with operation. It is mainly a guide for the front end of the barrel and adds surface area for the gas to push against.
The buffer won't do anything until the bolt hits it in recoil. Thats a bit late to change any of the unlocking characteristics.

The earlier style bolt catch won't help any more than the later type. Its weight and inertia damp the oscillation of the locking wedge by smacking it as its locking. It doesn't really change the timing of the unlocking. That is controlled by the recoiling barrel hitting the cam that pushes the rollers inward. None of these parts affect that timing.

The only suggestion I can see as a possibility are using a booster cone with a larger diameter hole. That will reduce the boost a little and may reduce bolt and barrel recoil velocity. The only thing is, with so many 42's out there running at 1100-1500 rpm I can't see this really helping with the issue. If the recoiling speed was really the problem all of those guns would be having it too. My guess is that it is a barrel related issue.

Frank

[Waffentag]

Thanks for the help, I had a couple of Nozzle Cones drilled out larger. This past weekend, I shot over 2000 rounds of 7.62 NATO and not a single case separated!

I did have a few Failures to Feed and a few times that they gun continued to fire a few rounds after letting up on the trigger.

So, I went to the next smaller size nozzle and the last 200 rounds were flawless. So I think that my problem is solved.

My only complaint is the very strong new spring that I put in makes it a real pain to pull the bolt all the way back to lock the bolt. I may try a used spring and see how it runs.

Thanks again, All,

PS, I ordered the 7.62x39 kit, should have it in a few weeks. I am really looking forward to trying that out