[chw2021]

Does anyone have an idea of the cup pressure of light ball ammo vs heavy ball? I am asking for a general measure not specific to any particular mfgr.year or country. The hungarian light ball load shoots wonderfully in all my Mosin rifles (no extraction or sticky bolt)... but any heavy ball in the same rifles will cause me to reach for a 2x4 to beat the bolt open and quite often tear the rim from the case. Is there a significant difference in velocity or chamber pressure between these different bullet weights? I am curious about surplus ammo (have not fired any commercial loads yet).

 

[ammolab]

CUP pressure of light ball and Heavy ball would be about the same Spec as originaly manufactured for both rounds were standardized to be used in ALL weapons so chambered.

BUT.... You are talking about 50+ year surplus mfg in some places where quality of components (powder) and quality control is not a given. Throw in variable storage conditions and Gee,...any "idea of pressure" would just be a wild guess.

Pressure may be a reason for your sicky bolt but other factors affect extraction too.

 

[chw2021]

The common factor is the heavy ball ammo. I am curious if there is a load difference other than the heavier bullet weight or a muzzle velocity difference that would (possibly) help to explain this. I am aware that the actual loading spec is just a "guideline" for much of the ammo produced and has no real meaning in the real world (sorta like the commie version of quality control); but the question remains as "why the heck does only heavy ball give multiple rifles the same problem". I have no clue so it's time to ask.

 

[cosmo05]

I never noticed a problem between heavy and light in my Mosins as far as the bolt, and I have over twenty of them. I DID notice a hard bolt opening on some steel case but the was either dirty chambers, very hot receiver from rapid fire. You may have a bolt or head space problem. The only difference between light and heavy is, the heavy takes a little longer to get down to barrel, so just a little more TIME of pressure is behind it, but any MORE pressure. Were you shooting steel cased or brass cased? I shoot brass cased HB and the bolt is smooth as butter, no matter which rifle I shoot it in. Steel case, that my be a little stiff sometimes even with a clean chamber but never hard enough I need to beat it open.

 

[chw2021]

That's one thing that I had not thought of.... I never claimed to be too bright. I am sure that I have leftovers in the range bag from where I noticed problems, I will check the cases.

 

[ammolab]

The only common factor for me with Heavy ball and bolt stickyness...is the HUNGARIAN heavy ball.

Polish, Russian, Bulgarian and maybe a few I forgot all shoot/extract fine in my various Rilfes.

Maybe the Hungarian has higher than standard pressure...or softer brass cases....or etc...others do OK for me.