Remember that bit about oiling bullets?

[RJW NZ]

and how the reduced friction in the chamber would create a lot of extra force on the bolt?
That really impressed me, and scared me all at the same time.
After a day at the range ('oorah, first of the spring season, first of many) one rifle has a chamber that clearly needs a clean up.
Can I clean this up or even polish it without running into lack of friction issues ala oil in the chamber?

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[Thunderbox]

and how the reduced friction in the chamber would create a lot of extra force on the bolt?
That really impressed me, and scared me all at the same time.
After a day at the range ('oorah, first of the spring season, first of many) one rifle has a chamber that clearly needs a clean up.
Can I clean this up or even polish it without running into lack of friction issues ala oil in the chamber?

We can cut through all the trolling that took place about this, and refer to an authoritative printed source: the Textbook Of Small Arms.

"Strength of Breach action.

Practically all military rifles are at least twice as strong as they need be, and many of them are ten times as strong. One great reason for this is that the cartridge case itself, when free from grease grips the wall of the chamber very tightly on firing and so relieves the dead weight thrust on the bolt head. This is very clearly shown when using the oiled-case method of pressure taking. The Mark VII cartridge is specified to give about 19 tons per square inch. If, however, the case is not dipped in oil it registers only about 10 or 12 tons per square inch. The "proof" cartridge for the .303 barrel is specified as about 24 tons, yet when fired without oiling the case it registers much less pressure on the bolt head than the service cartridge properly oiled."

etc

(going on to talk about the strength - or supposed weakness - of the SMLE rear-locking action)

"With good cases the S.M.L.E. can safely fire a few rounds at as much as 30 tons per square inch pressure whereas hardly any rifle using a rimless cartridge can stand one round at such an excessive pressure."

So a few points to note:

1. Service ammunition was assumed to be oiled. (Cleaning and oiling ammunition was in fact a standard battle preparation activity);

2. "Dry" ammo as used by most modern civilian shooters exerts less than 60% of the pressure on the bolt than was assumed for normal service conditions, less than 50% of the normal proof load - and perhaps less than 30% of the "real" tolerance of the rifle.


This isn't quite a direct answer to your question, because you are worried about "adhesion" of the case to the chamber wall. This is discussed elsewhere in the ToSA, but you can probably safely assume that the millions of rounds they used in testing would have been fired from rifles in proper military condition - i.e. with clean, polished chambers.

[RJW NZ]

thanks, I get it...thats a relief,

[louthepou]

I've had sticky empty cases issues with a Mosin Nagant last year. Once I cleaned the chamber really, really well, the issue was gone.

Lou

[jmoore]

I've had sticky empty cases issues with a Mosin Nagant last year. Once I cleaned the chamber really, really well, the issue was gone.

Lou

Was the issue resolved long term, or do you have to rigorously clean the chamber after every shoot? Wondering if its due to laquered cases or some other culprit. Folks seem to have this problem often w/ Mosins, however it hasn't struck me yet. Might be best replied in the Soviet weapons forum, though.

[Stevo]

Was the issue resolved long term, or do you have to rigorously clean the chamber after every shoot? Wondering if its due to laquered cases or some other culprit. Folks seem to have this problem often w/ Mosins, however it hasn't struck me yet. Might be best replied in the Soviet weapons forum, though.

It's generally a lacquer thing. I've seen it happen once in a VZ58 as well.

[jmoore]

Funny thing, that. I shoot lots of lacquered 7.62x39 and 54r w/o dramas.

[Stevo]

Funny thing, that. I shoot lots of lacquered 7.62x39 and 54r w/o dramas.

Do you run clean the chamber when you clean the bore? Do you get the rifle good and hot when you shoot it?

Not doing the former and doing the latter will make it more likely to happen.

[Alan de Enfield]

I tried some Barnaul 7.62x51 and apart from about 25% + failure to fire the lacquered cases caused no end of 'stickyness' problems in extraction - particularly after a few rounds and the barrel / chamber started to warm up.

Ended up giving away about 80 rounds. Absoulute P.I.T.A

[Alfred]

I've seen posts about a similar problem of laquered 7.62x51 cases, these were a particular German lot headstamped MEN or something like that.
The people discussing these seemed to conclude that the cartridges were intended for the roller locked rifles with the chambers fluted to provide a gas cushion to prevent the case from grabbibg the chamber wall. The heat of discharge softened the laquer, but in the auto rifle it had no deletrious effect. The seconds in sat in a bolt action chamber on the otherhand would let the laquer grip the chamber.

Perhaps some 7.62x54r ammo intended for MGs or the Dragonov had a similar coating.

As for oiled cartridges testing recounted in Reynolds Lee Enfield book suggests that oil caused very little problem unless a large glop of it was between bullet and chamber neck, but water on the cases could cause a greater increase in pressures since water is incompressable. If the case neck can't expand to release the bullet chamber pressures go up. Bullet upset begins before the bullet leaves the case.

BTW
Colonel Jim Crossman, noted authority on international competition and son of Captain E C crossman, was one of the expert witnesses involved in determining the cause of the Enfield breech blow out that killed a hunter in the US in the 1960's.
I haven't found my original source yet but did find and article written by Crossman in which he mentions the case.
The ammunition was manufactured by Federal, it was a common closed base hunting bullet not the open base tublar jacket bullet or Dum Dum.
The base of the recovered jacket was blown inwards, the core blown out.

Similar core blowouts or blow throughs were common with the 1903 loading of the US .30 loaded with hot burning double base powders. Erosion was determined to be the cause.
Record found here.
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