www.MG42.us

I bought all of the parts to get my M53 semi shooting 308. I also bought some new german 7.62 ammo. 3 rounds barely held the pressure and 4th one blew up, blew open the breech door and busted out extractor from the bolt, I felt the pressure against my face, good that I wear protection.
Now what is going on here? the barrel that I bought is from MG3 and there is a cut out, so there is nothing supporting the cartridge about 4mm to the end, need expert advice please.

https://s25.postimg.org/ipfk4gn8v/mg3ammoproblem.jpg

Also I decided to replace my rotten Yugo 8mm barrel with new Green Mountain chrome lined one. After 10 rounds , markings start appearing near the end of cartridge and I get fail to eject and primers become unstable. I have shot Yugo 8mm from my old barrel without issues. I compared and everything looks the same as my old Yugo barrel visually. So once the barrel heats up I get these problems, I wonder what is going on? Something going out of spec?

https://s25.postimg.org/u323fnxrj/green ... roblem.jpg

Why in the world is the end of the barrel chambered so deep? There is no way that the case can be supported by the bolt so you have the end of the cartridge hanging out there with no support. Take a look at the chamber at the end of your Yugo barrel to see what I mean. DO NOT SHOOT your gun with that barrel again or it will pop the case again this time causing you damage. Harry

messerschmittfan is absolutely correct. With that much of the chamber missing, I'm surprised the first three shots didn't blow too. Looks like that barrel is scrap. Where did you get it?

jbaum wrote:messerschmittfan is absolutely correct. With that much of the chamber missing, I'm surprised the first three shots didn't blow too. Looks like that barrel is scrap. Where did you get it?

At the gun show. The cut seems to be factory, have you ever seen mg3 barrel like that? What is your opinion on my 8mm shells?

Here is a pic of one of my surplus MG3 barrels.

My advise is to use surplus barrels and check them for head space.
Glad you are OK BTW.

Der Alder wrote:My advise is to use surplus barrels and check them for head space.
Glad you are OK BTW.

Also I got two recuperators, both Yugo and they don't compress flush, the plunger stops with about 5mm still to go.

hakentt wrote:

Der Alder wrote:My advise is to use surplus barrels and check them for head space.
Glad you are OK BTW.

Also I got two recuperators, both Yugo and they don't compress flush, the plunger stops with about 5mm still to go.

That sounds about right...recups of all types including the MG3, the head does not fully compress flush with the tube. The question on them always is if the spring rate is still in spec.

Der Alder wrote: That sounds about right...recups of all types including the MG3, the head does not fully compress flush with the tube. The question on them always is if the spring rate is still in spec.

According to the manual it should be flush and barrel should be stopped by the cam and not the recuperator.

viewtopic.php?t=5681

Or jbaum did not translate well from German.

by jbaum » Sun Jul 22, 2007 5:38 pm

"The Barrel strikes on the front side of the Unlocking Cams and is pushed again forward by the Recuperator."

That's a line from the MG3 manual that I've almost finished translating. It's on page 241/2, second paragraph from the ZDv 3/14 manual, which is available for free download in its original German on my website Links page ( http://www.GermanManuals.com/Links.html ). The English translation of this manual should be done in about a week.

hakentt wrote:

jbaum wrote:messerschmittfan is absolutely correct. With that much of the chamber missing, I'm surprised the first three shots didn't blow too. Looks like that barrel is scrap. Where did you get it?

At the gun show. The cut seems to be factory, have you ever seen mg3 barrel like that? What is your opinion on my 8mm shells?

No, I never saw any barrel with the chamber drilled like that. 8mm shells look near ready to blow. Did you check headspace?

jbaum wrote: 8mm shells look near ready to blow. Did you check headspace?

I checked it face of the bolt to the barrel has 0.5mm clearance with rollers fully locked, the same as my old yugo. If headspace was bad then it would show on first 10 rounds? Do you have automotive feeler gauges? Can you take your best barrel bolt heat and jam it together and give me a reading?

hakentt wrote:

jbaum wrote: 8mm shells look near ready to blow. Did you check headspace?

I checked it face of the bolt to the barrel has 0.5mm clearance with rollers fully locked, the same as my old yugo. If headspace was bad then it would show on first 10 rounds? Do you have automotive feeler gauges? Can you take your best barrel bolt heat and jam it together and give me a reading?

I don't think head spacing is your issue here, it just looks like it is ridiculously countersunk. The countersink won't effect where the shoulder in the chamber sits in relation to the bolt face. Your simply missing the back of the chamber but the depth of the chamber is likely correct, not that it would even matter if it isn't at this point.

hakentt wrote:

Der Alder wrote: That sounds about right...recups of all types including the MG3, the head does not fully compress flush with the tube. The question on them always is if the spring rate is still in spec.

According to the manual it should be flush and barrel should be stopped by the cam and not the recuperator.

viewtopic.php?t=5681

by jbaum » Sun Jul 22, 2007 5:38 pm

"The Barrel strikes on the front side of the Unlocking Cams and is pushed again forward by the Recuperator."

That's a line from the MG3 manual that I've almost finished translating. It's on page 241/2, second paragraph from the ZDv 3/14 manual, which is available for free download in its original German on my website Links page ( http://www.GermanManuals.com/Links.html ). The English translation of this manual should be done in about a week.

I was talking about the recuperator's head vs recuperator tube, (the recup itself) not the barrel and its relation to the recuperator.

Sw1ngK1ng wrote:

hakentt wrote:

jbaum wrote: 8mm shells look near ready to blow. Did you check headspace?

I checked it face of the bolt to the barrel has 0.5mm clearance with rollers fully locked, the same as my old yugo. If headspace was bad then it would show on first 10 rounds? Do you have automotive feeler gauges? Can you take your best barrel bolt heat and jam it together and give me a reading?

I don't think head spacing is your issue here, it just looks like it is ridiculously countersunk. The countersink won't effect where the shoulder in the chamber sits in relation to the bolt face. Your simply missing the back of the chamber but the depth of the chamber is likely correct, not that it would even matter if it isn't at this point.

He had a question too about the 8mm barrel and that sounds like a HS issue, which is why we mentioned that...the .308 countersunk barrel is simply junk and way out of spec.

Der Alder wrote: I was talking about the recuperator's head vs recuperator tube, (the recup itself) not the barrel and its relation to the recuperator.

I was talking about recup head vs recup tube. Booth of mine do compress to the end, it will appear that it stops about 5mm to the end but if I put my whole weight behind it, it will compress. Do you know why is the MG3 barrel counter sunk like that, is it for blank ammo only?

When you say 8mm barrel has HS issue, then is it too tight or too lose?

I looked at all five of my MG42's and one M53 barrels. I have one Austrian 7.62x51 NATO conversion units along with six spare barrels in 7.92x57 mm WWII German barrels and two Israeli 7.92x57 mm chrome lined barrels and NONE of them have the barrel so deeply countersunk. I do not think there is a problem with headspace as the cartridge would be supported by it's neck and could be fired. I really think that that barrel was counter sunk at least twice what it should have been. DO NOT SHOOT anything out of it. Just my thoughts Harry

On my 8mm green mountain barrel, checking headspace visually. I removed the extractor and with bolt facing down on the barrel I get no visual clearance with rollers fully locked up, when I turn the barrel around now bolt hangs down there is a 0.5mm gap and I can see the light, rollers are still locked, so the only slack is in the cam and rollers. Can anybody do the same test on their good known combination and tell me if you get the same result.

Headspace is not measured by the gap between the bolt face and chamber face. That measurement is only indirectly related to headspace. I wrote a detailed explanation of properly checking headspace on the 42 on here years ago. Do a search.

jbaum wrote: I wrote a detailed explanation of properly checking headspace on the 42 on here years ago. Do a search.

Can't find anything about headspace, bunch of worthless threads come up. Can you please do the same check I did and report here?