Had an odd 1st range outing with Finn M39.

[offthepaper]

So today I took a recently purchased Finn M39 to the range. The rifle in question is a '42 SKY with 100% blueing and a War time stock thats in good (?) condition.
I had cleaned the rifle/chamber/bore/trigger group when I got it to get rid of any cosmo residue.
Anyway, today i load the magazine with 5 rds and go to close the bolt and the bolt handle will not cycle down . The only ammo I had were steel cased Polish 54R and tried several different boxes, but none would allow the bolt to close. Had to pck it in and call it a day.
When I got home I tried a round of some of my handloads for my other Finns (I have 5), the round chmbered without any problem. I got my Micro out and measured the thickness of the rim (where the round headspaces on) and found the Polish steel case meausred in at .068 while the Privi brass that I reloaded with has a rim thickness of .056.
What surprises me is that the Polish ammo chambers without any problem in all my other Finns.
Was the machining of the chambers in the MN's that widely varied, or do I just have a particularly tight one? Anyone else have a problem chambering specific ammo in their MN?

 

[GD]

I have had similar problems with Albanian 7.62x54. This ammo has varying thickness in the rims. Most of my mosins will take the thicker rims and a few will only close with much difficulty. I bet a bolt out of one of your other mosins will work in your M39.
BTW, I too have a 1942 SKy M39 and it is one of my favorite rifles - accurate with a smooth two stage trigger. It however, looks like it went through hell in war time Finland.

 

[stubbicatt]

You might invest in a coin style headspace gage and see whether that is an issue with your new rifle. Could also be that cosmoline has built up on the breechface of the barrel. It is really hard to get in there to get that out.

As far as interchanging bolt heads, I would proceed with caution and only with the headspace gage at hand.