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Yugo 8MM M76 chamber question.

Slamshot

Plastic
Joined
Feb 25, 2019
Hi,
Hew member question.
I purchased a M76 rifle kit a few years ago which included the barrel.
The barrel chamber has a problem. When a cartridge is inserted it does not go far enough in to the chamber.
The extractor groove on the cartridge lacks about 1/16" to seat.
I painted a couple of cartridge necks with dye including a portion of the projectile and forced it to seat.
I removed the cartridge and took some pics of the dye transfer, which I have Included in the post.
It is obvious that the chamber was incorrectly cut.
My question is, does it need re-cutting the chamber, or does the throat need re-cutting?
I checked the headspace with gages, which is ok. Also I used new steel case, and some circa 1950 Greek ammo.

M76-4.jpgM76-5.jpg



Thanks for your help,
 
That looks like the dye transfer was on the neck area. What is the source of the barrel? If it is not stock, it may have been cut with a tight neck. I'd cast it with cerrosafe and measure the cast to figure out what's going on here.
 
That looks like the dye transfer was on the neck area. What is the source of the barrel? If it is not stock, it may have been cut with a tight neck. I'd cast it with cerrosafe and measure the cast to figure out what's going on here.

Thanks for your reply,

Yes, I didn't take photos of the cartridges, but the die was transferred from the area where the bullet is crimped to the neck.

The barrel was a take-off that came with the kit.
I have heard from some members at the "AK Forum" that the barrel was made by Green Mountain Barrels, however there are no markings.

I have ordered cerrosafe from Brownells and plan to cast the chamber along a Mauser 24/47 for comparison.

Green Mountain has that barrel for about $200.00, but I hope to save it if possible.


Thanks again,
 
Kind of a silly question, but are you sure about the dimensions of the test cartridge you used?

-Ron

Hi,

Didn't measure, but I used a couple out of same box.
Should be ok (I think), because I have used them in another Mauser.

Regards,
 
I would not trust your layout die test on a surplus cartridge, Your on the right track with cerrosafe but you also need a proper set of headspace gauges. I think that you'll end up renting a 8mm reamer and cleaning up the chamber.
Are you sure this is not a short chambered barrel that you finish ream with a pull through reamer after assembly? I didn't think GM was making fully finished ak type barrels as the hs is all over the place on these guns
That said worst case scenario is that you document what you find with the cerrosafe and gauges, and contact GM. They are a reputable company and if they cut the chamber to they will make it right.
 
I would not trust your layout die test on a surplus cartridge, Your on the right track with cerrosafe but you also need a proper set of headspace gauges. I think that you'll end up renting a 8mm reamer and cleaning up the chamber.
Are you sure this is not a short chambered barrel that you finish ream with a pull through reamer after assembly? I didn't think GM was making fully finished ak type barrels as the hs is all over the place on these guns
That said worst case scenario is that you document what you find with the cerrosafe and gauges, and contact GM. They are a reputable company and if they cut the chamber to they will make it right.

Good Evening,

At least it is evening for me.
I have just read your post, and agree. I have checked the headspace with go and field gages.
I pulled bullets from two cartridges and measured for comparison, which measure the same. I also did the same to two new manufacture steel case cartridges. These also have the same dimensions.

All of the cases, without bullets, will fit the chamber.
It appears, if I understand correctly, that the throat is dimensioned incorrectly.
At this point, as you stated, I will use Cerrosafe and compare the dims with the CIP dims for the chamber.
I will probably end up renting a reamer, as you suggested.

Thanks for your response,
 








 
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