Well you Mosin lovers read this

[ldp4570]

I still say that a hard bolt is usually attributed to high pressure for whatever reason. Here's a link you might check out. I noticed that it states the yellow tip are "high pressure" proof loads and the black bullets are "increased loads" which would explain some of the teeth jarring.http://7.62x54r.net/MosinID/MosinAmmoID01.htm

That may be true, and the ComBloc countries are not known for the best QC, yet I have to question yellowtip to being proof loads since they box it like all their other 7.62X54R. Here in the US proof loads are manufactured in extreamly small quantities, and very rarely see the outside of where the firearm is manufactured and tested due to the fact that it could be ugly if it got into the wrong gun. Its also one of the reasons I don't shoot any surplus in my 91/30PU. I want to enjoy her, not see if I can blow her up.

As to shooting a 91/30 pattern rifle enough to get the rifle hot enough to melt the laquer off the casings to jam the bolt, well you got a stronger shoulder than I do!

 

[Sniper John]

A problem with laquered ammo in a Mosin would not necessarily be from rapid fire. What happens with that type of ammo in my AR15 for example is from repeated firing over time. The laquer starts to build up over time in the chamber and will cause rounds to stick with very little firing. A good scrubbing of the chamber can correct it.

Also the yellow tip ammo is not a machine gun designation. If the ammo is Russian it is a heavy ball designation. Same code for most countries, but may not be the same for all. Heavy Ball is actually the correct bullet for that rifle and is what shoots best out my my original 91/30 Sniper.

But I prefer to shoot the silver tip or equivalent which is a light ball designation and steel core. It is a little easier on the shoulder.

 

[Fly]

I was also going to bring up the head space problem.The QC thing is also threw.
You must remember Russians were fighting the Germans in there back yard &
trying to put out guns as fast as possible.

 

[tinfinger]

Stiff bolt lift in MN; I recall the theory is that there are two factors: steel cases that don't contract as much as brass after firing, and the laquer on the steel cases heating up, transferring to the chamber walls and eventually making the chamber tight. I have shot steel case surplus and this seems plausible; bolt lift get progressively stiffer then I'll run a chamber brush and it goes away.

I have some brass case 7.62x54R but haven't had a chance to try it yet. If there is no bolt stiffness with unlaquered brass cases then there it is.

BTW, before shooting my MN I did clean the bolt and the chamber. This is a Finn M39 and really didn't need it. It seemed well cared for.

But the greasing of the bolt cam surfaces sounds like a great idea!

 

[Sniper John]

If you did not already know it. Bore diamters can be all over the place with surplus rifles, but one thing with your M39 is that the Finn'd rifles (with some exceptions) where barreled with a smaller diameter bore than the original Russian Barrel. Then the chambers were reamed to lengthen the throat to allow use of not just the Finnish ammo, but also the Russian made ammo having the larger diameter bullet.
If your M39 has the D designation on it, it has had the throat lengthened as most did.