Mosin Nagant Bolt Head issue


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mookiie
October 2, 2012, 04:54 PM
My issue is this. I have a mosin Nagant that I am having trouble closing on cartridges. I looked at a number of things that may have bveen the cause and now I have identified the issue. Great you say what do you need us for? Well please take a look at the picture below.

http://i1246.photobucket.com/albums/gg605/Mookiie2005/Mobile%20Uploads/2012-10-02_15-27-13_208.jpg

So the issue is the bolt head rim that surrounds the cartridge is slightly bent inwards towards where the rounds is held. On the very opposite side of the extractor the walls of the bolt head rim have been skewed slightly inwards. You maybe able to see it better in this picture.

http://i1246.photobucket.com/albums/gg605/Mookiie2005/Mobile%20Uploads/2012-10-02_15-28-06_840.jpg

Can anyone help explain how I could bend them out again to eliminate the issue?

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rcmodel
October 2, 2012, 05:25 PM
Judging from the blue discoloration on the rim?
Looks like someone purposely heated it red hot and bent it in at some point.

Perhaps a misguided attempt to get more positive extractor hook purchase??

Was it me?
I probably would not try to bend it back again, as it might break clear off depending on whether the heat annealed it, or Bubba dunked the hot bolt in cold water to cool it off.

I think what I would do is very carefully use a Dremel sanding drum or fine stone to open it on the inside edge where bent, enough for proper operation.

If that fails and extractor issues come back?
Time to replace the bolt head.
https://www.libertytreecollectors.com/productcart/pc/viewPrd.asp?idproduct=469


rc

Cosmoline
October 2, 2012, 05:47 PM
Just get some new bolt heads and fit using go/no go gauges.

dirtyjim
October 2, 2012, 05:52 PM
I could chuck it up in the lathe & roll it back out but a new bolt head with the extractor is under $20.
so that would be your easiest fix

mookiie
October 2, 2012, 06:46 PM
OK I have go/no go guages on the way, and a new bolt-head. Could someone point me to a resource on head-spacing? I am not very familiar with this process yet.

Cosmoline
October 2, 2012, 09:36 PM
Well just see if the new bolt head is good to go on the gauges. You may get lucky.

mookiie
October 2, 2012, 11:36 PM
ok so the bolt should close on the go guage and not close on the no-go guage is this correct?

gyvel
October 3, 2012, 01:14 AM
ok so the bolt should close on the go guage and not close on the no-go guage is this correct?

Yup.

Cosmoline
October 3, 2012, 02:46 AM
I'm not positive, but I'm pretty sure the arsenals would just have a box of bolt heads and mix and match to get a good one when doing replacements. I suspect that's why you see so many parts-out bolt bodies.

mookiie
October 4, 2012, 09:07 PM
Bolt head arrived and has been swapped out! Just waiting for the head-spacing gauges :banghead: Hope they get here before Saturday!

rcmodel
October 4, 2012, 09:22 PM
Quick, dirty, and cheap Mossy headspace check.

Max SAAMI rim thickness of the 7.62x54 Russian is .064".
Minimum headspace is also .064", so the thickest rimmed cartridge you should ever run into will still allow the bolt to close on it.
Get some ammo and measure the rims, then subtract what you get from .064".

You may have to measure the case length with a dail caliper, then measure to the front of the rim and subtract the differance due to those goofy rounded Russian case heads.

Then get a roll of Scotch Magic tape.
Each thickness of tape is very close to .0015" thick, so two layers = .003", etc, etc.
(Brass or steel .002" shim stock from the auto parts place also works very well)

Maximum headspace on the rifle is .068".
So, if you find a case average of .063" rim, adding three layers (.0045" of scotch Magic tape to the case head should still allow the bolt to close.

Adding four (.006") or more layers should not allow it to close.


But in actual fact, excess headspace is not the end of the world it is made out to be.
If a case separates due to excess headspace, it breaks well inside the chamber where the case web taper ends.
That allows the remaining rear section of the case to still seal the chamber sufficiently to prevent catastrophic gas escape.

Broken cases were so common 100 years ago that solders were issued "broken case extractors" in the cleaning kits to get the broken cases out and continue shooting.

Weren't no big deal until the Internet told us it was.

It is only a big deal now if you reload and have to buy new brass all the time due to case head separations.

rc

mookiie
October 4, 2012, 09:50 PM
Thanks RC! I want to see if I can use your method above to determine if the headspacing is OK and than check it again once the gauges get here. To see if it comes to the same conclusions. Not planning to fire until I am convinced the headspacing is good, not worth risking on a 100 dollar rifle in my opinion. Thanks again for the awesome info and methodology!

mookiie
October 5, 2012, 03:59 PM
Thanks everyone for your help! The gauges arrived today and the bolt closed on go but not on the no go. That is great because when I used the scotch tape method described by rcmodel it closed on 4 layers of tape with resistance but not five, so I was a little worried. Thanks again everyone!

rcmodel
October 5, 2012, 04:24 PM
Glad it all worked out.

Sorry to hear the tape method lead you slightly astray.

But it is not very scientific like I said.

Still, 4 layers with "slight resistance" would have been good to go IMO.
Tape is pretty soft & compressable when you got a big bolt cam working on it!

rc

mookiie
October 5, 2012, 06:52 PM
Still, 4 layers with "slight resistance" would have been good to go IMO.

You are right, I did meet slight resistance until I really pushed the bolt down and forced it. Plus when I took the tape off you could really see that it had been squeezed into the caliber lettering on the case as well as the primer pocket (it was an empty case), i reasoned that this could have been why it closed with force. So I was pretty sure it was good to go just not positive. Thanks again!

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