Mosin Nagant Chamber

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  • Last Post 13 May 2017
alco posted this 03 May 2017

First off, I love shooting my ole Mosin.  It's a fun gun to shoot with reduced loads.

I have noticed over the past few outings with my Mosin that out of 25 loads, 5 or 6 will be hard to chamber and 1 or 2 won't chamber !!!.

All bullets resized and reloaded with same dies using the same bullet at the same time.  The chamber is clean when I start shooting.  I shoot the Lee C312-185-1R with GC over 8.2 / BE sized to .311.  In my rifle it's a nose riding bullet..  The bullet gets a light coating of LLA.

What's causing this ???

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Ken Campbell Iowa posted this 03 May 2017

hi alco ... over simplified, it is probably just tolerance stackup in the cartridge assembly  ...  the direct approach would be to put dykem or nail polish or paint on the cartridge that doesn't chamber .....including bullet and all of brass .... then gently try to chamber and then gently remove and see what rubs.

a less direct way would be to measure suspect areas .... start with case neck diameter of the offending loaded rounds ... maybe different brands or lots of brass .... then lengths of the brass .... then the roundness of the bullets ... even with name-brand molds it is common to see 0.003 runout ... they shoot better than they look, usually .

check that the bullets are all seating the same ... if light neck tension a sticking bullet might be seated out further .

also note that the  same offending cartridges should repeat the hard chambering .... so that it is not some hangup with the rifle itself ... extractor or firing pin assy binding etc .

just some thoughts.  let us know what you find ... or if it remains a mystery ...

ken

 

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Eutectic posted this 03 May 2017

When looking for binding the best thing I have found is Dry Erase markers for use on white boards.

I would also carefully check the nose diameter on the bullets. If the mold does not close fully you can get a larger diameter bullet which will not chamber.

Using the marker should find the cause.

Steve

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Larry Gibson posted this 03 May 2017

How are you sizing the cases;

 

Full length sizing?

Partial sizing with a FL die?

 

With either of the above the side of the case is getting pushed back in which bumps the shoulder forward.

Or neck sizing?

 

Neck sizing is best.  I have been NSing my 7.62x54R cases using with cast bullet loads for years w/o having to FL or partial size due to chambering problems.  I use a slightly shortened Redding 284 Winchester bushing die with appropriate size bushing to give .002 - .003 neck tension on cast bullets of .312 to .316 diameter.  I also use a Lee .308W collet die with a 1/2" washer over the 7.62x54R case for use with jacketed bullets in my M91/30 Sniper.  The Lee collet die is adjusted to give the same .002 - .003" neck tension for Sierra 174 MKs.

 

Also does the seating die crimp also?

If the above is not the problem then you may have the seating die adjusted in the press too far so the crimp is causing some cases with and OAL too long to slightly buckle at the shoulder.  That will definitely give the chambering problems you mention.  Solution is to trim all the cases to the same OAL or back the seating die out so the case mouth does not hit the crimp portion of the seating die.

 

LMG

 

Concealment is not cover.........

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alco posted this 13 May 2017

I finally solved it, I think............The nose of some of my bullets were greater than .301.  They were as much as .308 !!!  I went through what bullets I had left and used the muzzle of my rifle as my go/no go gauge.  The ones that wouldn't go in the muzzle went back in the pot.  I loaded up the good ones and off to the range..............No problems with the bullets.

The bad / oversize bullets gave no indication of being oversize.  The mold separation line was barely visible.  Usually if the mold doesn't close completely it's very obvious.

I have now noticed that sometimes not all of the bullets are feeding correctly from the magazine.  If the extractor doesn't pickup the rim as it's fed into the chamber, the bolt WILL NOT CLOSE.  Has anyone else had this problem ???

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Larry Gibson posted this 13 May 2017

"I have now noticed that sometimes not all of the bullets are feeding correctly from the magazine.  If the extractor doesn't pickup the rim as it's fed into the chamber, the bolt WILL NOT CLOSE. " 

Are you referring to a Mosin Nagant with that question?  MNs are basically push feeds and the extractor is supposed to snap over the rim as the bolt is closed.  The cartridge rim doesn't slip up under the extractor during feeding from the magazine.

 

LMG

 

Concealment is not cover.........

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Wineman posted this 13 May 2017

My experience with bore riding is that if they slip fit at the muzzle they are not as accurate as ones that don't slide in. If the noses are casting large, the bases are too, but you said they are sized to 0.311". (small for any MN I have had my hands on). Fatter bases would give you fatter necks. If you pull the fat nose bullets, can you chamber the empty brass? You might be getting some fouling build up at the chamber mouth. When the MN's were in their sales heyday (10 years ago) many complained of rough and or cosmo filled chambers. It is possible that some has melted and moved around, causing the issue. AR shooters get a carbon ring that can cause chambering issues. I would give it a good chamber cleaning, maybe a M14 USGI chamber brush would help. I had a 1936 Tula M 91/30 a Spanish Civil war vet, that needed a 0.316 bullet but the chamber neck had issues unless I turned the brass pretty thin.

 

Dave

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